diff --git a/src/main/java/org/lmdbjava/BufferProxy.java b/src/main/java/org/lmdbjava/BufferProxy.java
index aff732b..f42da7f 100644
--- a/src/main/java/org/lmdbjava/BufferProxy.java
+++ b/src/main/java/org/lmdbjava/BufferProxy.java
@@ -21,6 +21,10 @@
 package org.lmdbjava;
 
 import static java.lang.Long.BYTES;
+import static org.lmdbjava.DbiFlags.MDB_INTEGERKEY;
+import static org.lmdbjava.DbiFlags.MDB_UNSIGNEDKEY;
+import static org.lmdbjava.MaskedFlag.isSet;
+import static org.lmdbjava.MaskedFlag.mask;
 
 import java.util.Comparator;
 
@@ -72,8 +76,24 @@ public abstract class BufferProxy<T> {
    * @param flags for the database
    * @return a comparator that can be used (never null)
    */
-  protected abstract Comparator<T> getComparator(DbiFlags... flags);
+  protected Comparator<T> getComparator(DbiFlags... flags) {
+    final int intFlag = mask(flags);
 
+    return isSet(intFlag, MDB_INTEGERKEY) || isSet(intFlag, MDB_UNSIGNEDKEY) ? getUnsignedComparator() : getSignedComparator();
+  }
+
+  /**
+   * Get a suitable default {@link Comparator} to compare numeric key values as unsigned.
+   *
+   * @return a comparator that can be used (never null)
+   */
+  protected abstract Comparator<T> getUnsignedComparator();
+  /**
+   * Get a suitable default {@link Comparator} to compare numeric key values as signed.
+   *
+   * @return a comparator that can be used (never null)
+   */
+  protected abstract Comparator<T> getSignedComparator();
   /**
    * Deallocate a buffer that was previously provided by {@link #allocate()}.
    *
diff --git a/src/main/java/org/lmdbjava/ByteArrayProxy.java b/src/main/java/org/lmdbjava/ByteArrayProxy.java
index 3fe8184..2066b67 100644
--- a/src/main/java/org/lmdbjava/ByteArrayProxy.java
+++ b/src/main/java/org/lmdbjava/ByteArrayProxy.java
@@ -20,14 +20,15 @@
 
 package org.lmdbjava;
 
-import static java.util.Objects.requireNonNull;
-import static org.lmdbjava.Library.RUNTIME;
+import jnr.ffi.Pointer;
+import jnr.ffi.provider.MemoryManager;
 
 import java.util.Arrays;
 import java.util.Comparator;
 
-import jnr.ffi.Pointer;
-import jnr.ffi.provider.MemoryManager;
+import static java.lang.Math.min;
+import static java.util.Objects.requireNonNull;
+import static org.lmdbjava.Library.RUNTIME;
 
 /**
  * Byte array proxy.
@@ -43,7 +44,10 @@ public final class ByteArrayProxy extends BufferProxy<byte[]> {
 
   private static final MemoryManager MEM_MGR = RUNTIME.getMemoryManager();
 
-  private ByteArrayProxy() {
+  private static final Comparator<byte[]> signedComparator = ByteArrayProxy::compareArraysSigned;
+  private static final Comparator<byte[]> unsignedComparator = ByteArrayProxy::compareArrays;
+
+    private ByteArrayProxy() {
   }
 
   /**
@@ -60,7 +64,7 @@ public static int compareArrays(final byte[] o1, final byte[] o2) {
     if (o1 == o2) {
       return 0;
     }
-    final int minLength = Math.min(o1.length, o2.length);
+    final int minLength = min(o1.length, o2.length);
 
     for (int i = 0; i < minLength; i++) {
       final int lw = Byte.toUnsignedInt(o1[i]);
@@ -74,15 +78,32 @@ public static int compareArrays(final byte[] o1, final byte[] o2) {
     return o1.length - o2.length;
   }
 
+  /**
+   * Compare two byte arrays.
+   *
+   * @param b1 left operand (required)
+   * @param b2 right operand (required)
+   * @return as specified by {@link Comparable} interface
+   */
+  @SuppressWarnings("PMD.CompareObjectsWithEquals")
+  public static int compareArraysSigned(final byte[] b1, final byte[] b2) {
+    requireNonNull(b1);
+    requireNonNull(b2);
+
+    if (b1 == b2) return 0;
+
+    for(int i = 0; i < min(b1.length, b2.length); ++i) {
+      if(b1[i] != b2[i]) return b1[i] - b2[i];
+    }
+
+    return b1.length - b2.length;
+  }
+
   @Override
   protected byte[] allocate() {
     return new byte[0];
   }
 
-  protected int compare(final byte[] o1, final byte[] o2) {
-    return compareArrays(o1, o2);
-  }
-
   @Override
   protected void deallocate(final byte[] buff) {
     // byte arrays cannot be allocated
@@ -94,8 +115,13 @@ protected byte[] getBytes(final byte[] buffer) {
   }
 
   @Override
-  protected Comparator<byte[]> getComparator(final DbiFlags... flags) {
-    return this::compare;
+  protected Comparator<byte[]> getSignedComparator() {
+    return signedComparator;
+  }
+
+  @Override
+  protected Comparator<byte[]> getUnsignedComparator() {
+    return unsignedComparator;
   }
 
   @Override
diff --git a/src/main/java/org/lmdbjava/ByteBufProxy.java b/src/main/java/org/lmdbjava/ByteBufProxy.java
index 2635167..ed3d71e 100644
--- a/src/main/java/org/lmdbjava/ByteBufProxy.java
+++ b/src/main/java/org/lmdbjava/ByteBufProxy.java
@@ -20,16 +20,17 @@
 
 package org.lmdbjava;
 
-import static io.netty.buffer.PooledByteBufAllocator.DEFAULT;
-import static java.lang.Class.forName;
-import static org.lmdbjava.UnsafeAccess.UNSAFE;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.PooledByteBufAllocator;
+import jnr.ffi.Pointer;
 
 import java.lang.reflect.Field;
 import java.util.Comparator;
 
-import io.netty.buffer.ByteBuf;
-import io.netty.buffer.PooledByteBufAllocator;
-import jnr.ffi.Pointer;
+import static io.netty.buffer.PooledByteBufAllocator.DEFAULT;
+import static java.lang.Class.forName;
+import static java.util.Objects.requireNonNull;
+import static org.lmdbjava.UnsafeAccess.UNSAFE;
 
 /**
  * A buffer proxy backed by Netty's {@link ByteBuf}.
@@ -51,6 +52,12 @@ public final class ByteBufProxy extends BufferProxy<ByteBuf> {
   private static final String FIELD_NAME_ADDRESS = "memoryAddress";
   private static final String FIELD_NAME_LENGTH = "length";
   private static final String NAME = "io.netty.buffer.PooledUnsafeDirectByteBuf";
+  private static final Comparator<ByteBuf> comparator = (o1, o2) -> {
+    requireNonNull(o1);
+    requireNonNull(o2);
+
+    return o1.compareTo(o2);
+  };
   private final long lengthOffset;
   private final long addressOffset;
   
@@ -107,13 +114,14 @@ protected ByteBuf allocate() {
     throw new IllegalStateException("Netty buffer must be " + NAME);
   }
 
-  protected int compare(final ByteBuf o1, final ByteBuf o2) {
-    return o1.compareTo(o2);
+  @Override
+  protected Comparator<ByteBuf> getSignedComparator() {
+    return comparator;
   }
 
   @Override
-  protected Comparator<ByteBuf> getComparator(final DbiFlags... flags) {
-    return this::compare;
+  protected Comparator<ByteBuf> getUnsignedComparator() {
+    return comparator;
   }
 
   @Override
diff --git a/src/main/java/org/lmdbjava/ByteBufferProxy.java b/src/main/java/org/lmdbjava/ByteBufferProxy.java
index 8eb95da..9983d76 100644
--- a/src/main/java/org/lmdbjava/ByteBufferProxy.java
+++ b/src/main/java/org/lmdbjava/ByteBufferProxy.java
@@ -27,6 +27,7 @@
 import static java.nio.ByteOrder.LITTLE_ENDIAN;
 import static java.util.Objects.requireNonNull;
 import static org.lmdbjava.DbiFlags.MDB_INTEGERKEY;
+import static org.lmdbjava.DbiFlags.MDB_UNSIGNEDKEY;
 import static org.lmdbjava.Env.SHOULD_CHECK;
 import static org.lmdbjava.MaskedFlag.isSet;
 import static org.lmdbjava.MaskedFlag.mask;
@@ -111,6 +112,14 @@ abstract static class AbstractByteBufferProxy extends BufferProxy<ByteBuffer> {
     protected static final String FIELD_NAME_ADDRESS = "address";
     protected static final String FIELD_NAME_CAPACITY = "capacity";
 
+    private static final Comparator<ByteBuffer> signedComparator = (o1, o2) -> {
+      requireNonNull(o1);
+      requireNonNull(o2);
+
+      return o1.compareTo(o2);
+    };
+    private static final Comparator<ByteBuffer> unsignedComparator = AbstractByteBufferProxy::compareBuff;
+
     /**
      * A thread-safe pool for a given length. If the buffer found is valid (ie
      * not of a negative length) then that buffer is used. If no valid buffer is
@@ -193,22 +202,13 @@ protected final ByteBuffer allocate() {
     }
 
     @Override
-    protected Comparator<ByteBuffer> getComparator(final DbiFlags... flags) {
-      final int flagInt = mask(flags);
-      if (isSet(flagInt, MDB_INTEGERKEY)) {
-        return this::compareCustom;
-      }
-      return this::compareDefault;
+    protected Comparator<ByteBuffer> getSignedComparator() {
+      return signedComparator;
     }
 
-    protected final int compareDefault(final ByteBuffer o1,
-                                       final ByteBuffer o2) {
-      return o1.compareTo(o2);
-    }
-
-    protected final int compareCustom(final ByteBuffer o1,
-                                      final ByteBuffer o2) {
-      return compareBuff(o1, o2);
+    @Override
+    protected Comparator<ByteBuffer> getUnsignedComparator() {
+      return unsignedComparator;
     }
 
     @Override
diff --git a/src/main/java/org/lmdbjava/Cursor.java b/src/main/java/org/lmdbjava/Cursor.java
index ed7c184..cb9130e 100644
--- a/src/main/java/org/lmdbjava/Cursor.java
+++ b/src/main/java/org/lmdbjava/Cursor.java
@@ -40,6 +40,8 @@
 import jnr.ffi.Pointer;
 import jnr.ffi.byref.NativeLongByReference;
 
+import java.util.Arrays;
+
 /**
  * A cursor handle.
  *
@@ -120,7 +122,7 @@ public void delete(final PutFlags... f) {
       txn.checkReady();
       txn.checkWritesAllowed();
     }
-    final int flags = mask(f);
+    final int flags = mask(true, f);
     checkRc(LIB.mdb_cursor_del(ptrCursor, flags));
   }
 
@@ -256,7 +258,7 @@ public boolean put(final T key, final T val, final PutFlags... op) {
     }
     kv.keyIn(key);
     kv.valIn(val);
-    final int mask = mask(op);
+    final int mask = mask(true, op);
     final int rc = LIB.mdb_cursor_put(ptrCursor, kv.pointerKey(),
                                       kv.pointerVal(), mask);
     if (rc == MDB_KEYEXIST) {
@@ -299,7 +301,7 @@ public void putMultiple(final T key, final T val, final int elements,
       txn.checkReady();
       txn.checkWritesAllowed();
     }
-    final int mask = mask(op);
+    final int mask = mask(true, op);
     if (SHOULD_CHECK && !isSet(mask, MDB_MULTIPLE)) {
       throw new IllegalArgumentException("Must set " + MDB_MULTIPLE + " flag");
     }
@@ -364,7 +366,7 @@ public T reserve(final T key, final int size, final PutFlags... op) {
     }
     kv.keyIn(key);
     kv.valIn(size);
-    final int flags = mask(op) | MDB_RESERVE.getMask();
+    final int flags = mask(true, op) | MDB_RESERVE.getMask();
     checkRc(LIB.mdb_cursor_put(ptrCursor, kv.pointerKey(), kv.pointerVal(),
                                flags));
     kv.valOut();
diff --git a/src/main/java/org/lmdbjava/Dbi.java b/src/main/java/org/lmdbjava/Dbi.java
index ef8ec31..c5be4f8 100644
--- a/src/main/java/org/lmdbjava/Dbi.java
+++ b/src/main/java/org/lmdbjava/Dbi.java
@@ -20,6 +20,17 @@
 
 package org.lmdbjava;
 
+import jnr.ffi.Pointer;
+import jnr.ffi.byref.IntByReference;
+import jnr.ffi.byref.PointerByReference;
+import org.lmdbjava.Library.ComparatorCallback;
+import org.lmdbjava.Library.MDB_stat;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
 import static java.util.Objects.requireNonNull;
 import static jnr.ffi.Memory.allocateDirect;
 import static jnr.ffi.NativeType.ADDRESS;
@@ -36,17 +47,6 @@
 import static org.lmdbjava.PutFlags.MDB_RESERVE;
 import static org.lmdbjava.ResultCodeMapper.checkRc;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Comparator;
-import java.util.List;
-
-import jnr.ffi.Pointer;
-import jnr.ffi.byref.IntByReference;
-import jnr.ffi.byref.PointerByReference;
-import org.lmdbjava.Library.ComparatorCallback;
-import org.lmdbjava.Library.MDB_stat;
-
 /**
  * LMDB Database.
  *
@@ -64,10 +64,18 @@ public final class Dbi<T> {
   Dbi(final Env<T> env, final Txn<T> txn, final byte[] name,
       final Comparator<T> comparator, final boolean nativeCb,
       final BufferProxy<T> proxy, final DbiFlags... flags) {
+    if (SHOULD_CHECK) {
+      requireNonNull(txn);
+      txn.checkReady();
+    }
     this.env = env;
     this.name = name == null ? null : Arrays.copyOf(name, name.length);
-    this.comparator = comparator;
-    final int flagsMask = mask(flags);
+    if(comparator == null) {
+      this.comparator = proxy.getComparator(flags);
+    } else {
+      this.comparator = comparator;
+    }
+    final int flagsMask = mask(true, flags);
     final Pointer dbiPtr = allocateDirect(RUNTIME, ADDRESS);
     checkRc(LIB.mdb_dbi_open(txn.pointer(), name, flagsMask, dbiPtr));
     ptr = dbiPtr.getPointer(0);
@@ -377,7 +385,7 @@ public boolean put(final Txn<T> txn, final T key, final T val,
     }
     txn.kv().keyIn(key);
     txn.kv().valIn(val);
-    final int mask = mask(flags);
+    final int mask = mask(true, flags);
     final int rc = LIB.mdb_put(txn.pointer(), ptr, txn.kv().pointerKey(), txn
                                .kv().pointerVal(), mask);
     if (rc == MDB_KEYEXIST) {
@@ -422,7 +430,7 @@ public T reserve(final Txn<T> txn, final T key, final int size,
     }
     txn.kv().keyIn(key);
     txn.kv().valIn(size);
-    final int flags = mask(op) | MDB_RESERVE.getMask();
+    final int flags = mask(true, op) | MDB_RESERVE.getMask();
     checkRc(LIB.mdb_put(txn.pointer(), ptr, txn.kv().pointerKey(), txn.kv()
                         .pointerVal(), flags));
     txn.kv().valOut(); // marked as in,out in LMDB C docs
diff --git a/src/main/java/org/lmdbjava/DbiFlags.java b/src/main/java/org/lmdbjava/DbiFlags.java
index 081fb80..7277b55 100644
--- a/src/main/java/org/lmdbjava/DbiFlags.java
+++ b/src/main/java/org/lmdbjava/DbiFlags.java
@@ -68,6 +68,15 @@ public enum DbiFlags implements MaskedFlag {
    * similar to {@link #MDB_INTEGERKEY} keys.
    */
   MDB_INTEGERDUP(0x20),
+  /**
+   * Compare the <b>numeric</b> keys in native byte order and as unsigned.
+   *
+   * <p>
+   * This option is applied only to {@link java.nio.ByteBuffer}, {@link org.agrona.DirectBuffer} and byte array keys.
+   * {@link io.netty.buffer.ByteBuf} keys are always compared in native byte order and as unsigned.
+   * </p>
+   */
+  MDB_UNSIGNEDKEY(0x30, false),
   /**
    * With {@link #MDB_DUPSORT}, use reverse string dups.
    *
@@ -86,9 +95,15 @@ public enum DbiFlags implements MaskedFlag {
   MDB_CREATE(0x4_0000);
 
   private final int mask;
+  private final boolean propagatedToLmdb;
 
-  DbiFlags(final int mask) {
+  DbiFlags(final int mask, final boolean propagatedToLmdb) {
     this.mask = mask;
+    this.propagatedToLmdb = propagatedToLmdb;
+  }
+
+  DbiFlags(final int mask) {
+    this(mask, true);
   }
 
   @Override
@@ -96,4 +111,8 @@ public int getMask() {
     return mask;
   }
 
+  @Override
+  public boolean isPropagatedToLmdb() {
+    return propagatedToLmdb;
+  }
 }
diff --git a/src/main/java/org/lmdbjava/DirectBufferProxy.java b/src/main/java/org/lmdbjava/DirectBufferProxy.java
index 62b4909..3bde81e 100644
--- a/src/main/java/org/lmdbjava/DirectBufferProxy.java
+++ b/src/main/java/org/lmdbjava/DirectBufferProxy.java
@@ -20,20 +20,20 @@
 
 package org.lmdbjava;
 
-import static java.lang.ThreadLocal.withInitial;
-import static java.nio.ByteBuffer.allocateDirect;
-import static java.nio.ByteOrder.BIG_ENDIAN;
-import static java.util.Objects.requireNonNull;
-import static org.lmdbjava.UnsafeAccess.UNSAFE;
+import jnr.ffi.Pointer;
+import org.agrona.DirectBuffer;
+import org.agrona.MutableDirectBuffer;
+import org.agrona.concurrent.UnsafeBuffer;
 
 import java.nio.ByteBuffer;
 import java.util.ArrayDeque;
 import java.util.Comparator;
 
-import jnr.ffi.Pointer;
-import org.agrona.DirectBuffer;
-import org.agrona.MutableDirectBuffer;
-import org.agrona.concurrent.UnsafeBuffer;
+import static java.lang.ThreadLocal.withInitial;
+import static java.nio.ByteBuffer.allocateDirect;
+import static java.nio.ByteOrder.BIG_ENDIAN;
+import static java.util.Objects.requireNonNull;
+import static org.lmdbjava.UnsafeAccess.UNSAFE;
 
 /**
  * A buffer proxy backed by Agrona's {@link DirectBuffer}.
@@ -42,6 +42,13 @@
  * This class requires {@link UnsafeAccess} and Agrona must be in the classpath.
  */
 public final class DirectBufferProxy extends BufferProxy<DirectBuffer> {
+  private static final Comparator<DirectBuffer> signedComparator = (o1, o2) -> {
+    requireNonNull(o1);
+    requireNonNull(o2);
+
+    return o1.compareTo(o2);
+  };
+  private static final Comparator<DirectBuffer> unsignedComparator = DirectBufferProxy::compareBuff;
 
   /**
    * The {@link MutableDirectBuffer} proxy. Guaranteed to never be null,
@@ -112,8 +119,14 @@ protected DirectBuffer allocate() {
     }
   }
 
-  protected int compare(final DirectBuffer o1, final DirectBuffer o2) {
-    return compareBuff(o1, o2);
+  @Override
+  protected Comparator<DirectBuffer> getSignedComparator() {
+    return signedComparator;
+  }
+
+  @Override
+  protected Comparator<DirectBuffer> getUnsignedComparator() {
+    return unsignedComparator;
   }
 
   @Override
@@ -129,11 +142,6 @@ protected byte[] getBytes(final DirectBuffer buffer) {
     return dest;
   }
 
-  @Override
-  protected Comparator<DirectBuffer> getComparator(final DbiFlags... flags) {
-    return this::compare;
-  }
-
   @Override
   protected void in(final DirectBuffer buffer, final Pointer ptr,
                     final long ptrAddr) {
diff --git a/src/main/java/org/lmdbjava/Env.java b/src/main/java/org/lmdbjava/Env.java
index db8b0f4..ae7e46c 100644
--- a/src/main/java/org/lmdbjava/Env.java
+++ b/src/main/java/org/lmdbjava/Env.java
@@ -20,6 +20,19 @@
 
 package org.lmdbjava;
 
+import jnr.ffi.Pointer;
+import jnr.ffi.byref.IntByReference;
+import jnr.ffi.byref.PointerByReference;
+import org.lmdbjava.Library.MDB_envinfo;
+import org.lmdbjava.Library.MDB_stat;
+
+import java.io.File;
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
 import static java.lang.Boolean.getBoolean;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static java.util.Objects.requireNonNull;
@@ -33,19 +46,6 @@
 import static org.lmdbjava.ResultCodeMapper.checkRc;
 import static org.lmdbjava.TxnFlags.MDB_RDONLY_TXN;
 
-import java.io.File;
-import java.nio.ByteBuffer;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Comparator;
-import java.util.List;
-
-import jnr.ffi.Pointer;
-import jnr.ffi.byref.IntByReference;
-import jnr.ffi.byref.PointerByReference;
-import org.lmdbjava.Library.MDB_envinfo;
-import org.lmdbjava.Library.MDB_stat;
-
 /**
  * LMDB environment.
  *
@@ -159,7 +159,7 @@ public void close() {
   public void copy(final File path, final CopyFlags... flags) {
     requireNonNull(path);
     validatePath(path);
-    final int flagsMask = mask(flags);
+    final int flagsMask = mask(true, flags);
     checkRc(LIB.mdb_env_copy2(ptr, path.getAbsolutePath(), flagsMask));
   }
 
@@ -388,17 +388,7 @@ public Dbi<T> openDbi(final byte[] name, final Comparator<T> comparator,
   public Dbi<T> openDbi(final Txn<T> txn, final byte[] name,
                         final Comparator<T> comparator, final boolean nativeCb,
                         final DbiFlags... flags) {
-    if (SHOULD_CHECK) {
-      requireNonNull(txn);
-      txn.checkReady();
-    }
-    final Comparator<T> useComparator;
-    if (comparator == null) {
-      useComparator = proxy.getComparator(flags);
-    } else {
-      useComparator = comparator;
-    }
-    return new Dbi<>(this, txn, name, useComparator, nativeCb, proxy, flags);
+    return new Dbi<>(this, txn, name, comparator, nativeCb, proxy, flags);
   }
 
   /**
@@ -583,7 +573,7 @@ public Env<T> open(final File path, final int mode,
         checkRc(LIB.mdb_env_set_mapsize(ptr, mapSize));
         checkRc(LIB.mdb_env_set_maxdbs(ptr, maxDbs));
         checkRc(LIB.mdb_env_set_maxreaders(ptr, maxReaders));
-        final int flagsMask = mask(flags);
+        final int flagsMask = mask(true, flags);
         final boolean readOnly = isSet(flagsMask, MDB_RDONLY_ENV);
         final boolean noSubDir = isSet(flagsMask, MDB_NOSUBDIR);
         checkRc(LIB.mdb_env_open(ptr, path.getAbsolutePath(), flagsMask, mode));
diff --git a/src/main/java/org/lmdbjava/MaskedFlag.java b/src/main/java/org/lmdbjava/MaskedFlag.java
index 9bdef63..242ca58 100644
--- a/src/main/java/org/lmdbjava/MaskedFlag.java
+++ b/src/main/java/org/lmdbjava/MaskedFlag.java
@@ -20,6 +20,11 @@
 
 package org.lmdbjava;
 
+import java.util.Arrays;
+import java.util.Objects;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+
 import static java.util.Objects.requireNonNull;
 
 /**
@@ -34,25 +39,58 @@ public interface MaskedFlag {
    */
   int getMask();
 
+  /**
+   * Indicates if the flag must be propagated to the underlying C code of LMDB or not.
+   *
+   * @return the boolean value indicating the propagation
+   */
+  default boolean isPropagatedToLmdb() {
+    return true;
+  }
+
+  /**
+   * Fetch the integer mask for all presented flags.
+   *
+   * @param flags to mask (null or empty returns zero)
+   * @return the integer mask for use in C
+   */
+  @SafeVarargs
+  static <M extends MaskedFlag> int mask(final M... flags) {
+    return mask(false, flags);
+  }
+
   /**
    * Fetch the integer mask for all presented flags.
    *
    * @param flags to mask (null or empty returns zero)
    * @return the integer mask for use in C
    */
-  static int mask(final MaskedFlag... flags) {
-    if (flags == null || flags.length == 0) {
-      return 0;
-    }
+  static <M extends MaskedFlag> int mask(final Stream<M> flags) {
+    return mask(false, flags);
+  }
+
+  /**
+   * Fetch the integer mask for the presented flags.
+   *
+   * @param onlyPropagatedToLmdb if to include only the flags which are also propagate to the C code or all of them
+   * @param flags to mask (null or empty returns zero)
+   * @return the integer mask for use in C
+   */
+  @SafeVarargs
+  static <M extends MaskedFlag> int mask(final boolean onlyPropagatedToLmdb, final M... flags) {
+    return flags == null ? 0 : mask(onlyPropagatedToLmdb, Arrays.stream(flags));
+  }
+
+  /**
+   * Fetch the integer mask for all presented flags.
+   *
+   * @param onlyPropagatedToLmdb if to include only the flags which are also propagate to the C code or all of them
+   * @return the integer mask for use in C
+   */
+  static <M extends MaskedFlag> int mask(final boolean onlyPropagatedToLmdb, final Stream<M> flags) {
+    final Predicate<M> filter = onlyPropagatedToLmdb ? MaskedFlag::isPropagatedToLmdb : f -> true;
 
-    int result = 0;
-    for (final MaskedFlag flag : flags) {
-      if (flag == null) {
-        continue;
-      }
-      result |= flag.getMask();
-    }
-    return result;
+    return flags == null ? 0 : flags.filter(Objects::nonNull).filter(filter).map(M::getMask).reduce(0, (f1, f2) -> f1 | f2);
   }
 
   /**
diff --git a/src/main/java/org/lmdbjava/Txn.java b/src/main/java/org/lmdbjava/Txn.java
index b6d2891..3092c7c 100644
--- a/src/main/java/org/lmdbjava/Txn.java
+++ b/src/main/java/org/lmdbjava/Txn.java
@@ -20,6 +20,8 @@
 
 package org.lmdbjava;
 
+import jnr.ffi.Pointer;
+
 import static jnr.ffi.Memory.allocateDirect;
 import static jnr.ffi.NativeType.ADDRESS;
 import static org.lmdbjava.Env.SHOULD_CHECK;
@@ -34,8 +36,6 @@
 import static org.lmdbjava.Txn.State.RESET;
 import static org.lmdbjava.TxnFlags.MDB_RDONLY_TXN;
 
-import jnr.ffi.Pointer;
-
 /**
  * LMDB transaction.
  *
@@ -55,7 +55,7 @@ public final class Txn<T> implements AutoCloseable {
       final TxnFlags... flags) {
     this.proxy = proxy;
     this.keyVal = proxy.keyVal();
-    final int flagsMask = mask(flags);
+    final int flagsMask = mask(true, flags);
     this.readOnly = isSet(flagsMask, MDB_RDONLY_TXN);
     if (env.isReadOnly() && !this.readOnly) {
       throw new EnvIsReadOnly();

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