diff --git a/control/bdalg.py b/control/bdalg.py
index 9d5aac654..b92496477 100644
--- a/control/bdalg.py
+++ b/control/bdalg.py
@@ -54,6 +54,7 @@
 """
 
 import scipy as sp
+import numpy as np
 from . import xferfcn as tf
 from . import statesp as ss
 from . import frdata as frd
@@ -221,18 +222,18 @@ def feedback(sys1, sys2=1, sign=-1):
     """
 
     # Check for correct input types.
-    if not isinstance(sys1, (int, float, complex, tf.TransferFunction,
-                             ss.StateSpace, frd.FRD)):
+    if not isinstance(sys1, (int, float, complex, np.number,
+                             tf.TransferFunction, ss.StateSpace, frd.FRD)):
         raise TypeError("sys1 must be a TransferFunction, StateSpace " +
                         "or FRD object, or a scalar.")
-    if not isinstance(sys2, (int, float, complex, tf.TransferFunction,
-                             ss.StateSpace, frd.FRD)):
+    if not isinstance(sys2, (int, float, complex, np.number,
+                             tf.TransferFunction, ss.StateSpace, frd.FRD)):
         raise TypeError("sys2 must be a TransferFunction, StateSpace " +
                         "or FRD object, or a scalar.")
 
     # If sys1 is a scalar, convert it to the appropriate LTI type so that we can
     # its feedback member function.
-    if isinstance(sys1, (int, float, complex)):
+    if isinstance(sys1, (int, float, complex, np.number)):
         if isinstance(sys2, tf.TransferFunction):
             sys1 = tf._convertToTransferFunction(sys1)
         elif isinstance(sys2, ss.StateSpace):
diff --git a/control/frdata.py b/control/frdata.py
index ff1663b15..313da12b2 100644
--- a/control/frdata.py
+++ b/control/frdata.py
@@ -49,6 +49,7 @@
 """
 
 # External function declarations
+import numpy as np
 from numpy import angle, array, empty, ones, \
     real, imag, matrix, absolute, eye, linalg, where, dot
 from scipy.interpolate import splprep, splev
@@ -219,7 +220,7 @@ def __mul__(self, other):
         """Multiply two LTI objects (serial connection)."""
 
         # Convert the second argument to a transfer function.
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             return FRD(self.fresp * other, self.omega,
                        smooth=(self.ifunc is not None))
         else:
@@ -245,7 +246,7 @@ def __rmul__(self, other):
         """Right Multiply two LTI objects (serial connection)."""
 
         # Convert the second argument to an frd function.
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             return FRD(self.fresp * other, self.omega,
                        smooth=(self.ifunc is not None))
         else:
@@ -272,7 +273,7 @@ def __rmul__(self, other):
     def __truediv__(self, other):
         """Divide two LTI objects."""
 
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             return FRD(self.fresp * (1/other), self.omega,
                        smooth=(self.ifunc is not None))
         else:
@@ -295,7 +296,7 @@ def __div__(self, other):
     # TODO: Division of MIMO transfer function objects is not written yet.
     def __rtruediv__(self, other):
         """Right divide two LTI objects."""
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             return FRD(other / self.fresp, self.omega,
                        smooth=(self.ifunc is not None))
         else:
@@ -449,7 +450,7 @@ def _convertToFRD(sys, omega, inputs=1, outputs=1):
 
         return FRD(fresp, omega, smooth=True)
 
-    elif isinstance(sys, (int, float, complex)):
+    elif isinstance(sys, (int, float, complex, np.number)):
         fresp = ones((outputs, inputs, len(omega)), dtype=float)*sys
         return FRD(fresp, omega, smooth=True)
 
diff --git a/control/lti.py b/control/lti.py
index ab7672d51..aeef5cbb1 100644
--- a/control/lti.py
+++ b/control/lti.py
@@ -12,6 +12,7 @@
 timebaseEqual()
 """
 
+import numpy as np
 from numpy import absolute, real
 
 __all__ = ['issiso', 'timebase', 'timebaseEqual', 'isdtime', 'isctime',
@@ -96,7 +97,7 @@ def dcgain(self):
 
 # Test to see if a system is SISO
 def issiso(sys, strict=False):
-    if isinstance(sys, (int, float, complex)) and not strict:
+    if isinstance(sys, (int, float, complex, np.number)) and not strict:
         return True
     elif not isinstance(sys, LTI):
         raise ValueError("Object is not an LTI system")
@@ -114,7 +115,7 @@ def timebase(sys, strict=True):
     set to False, dt = True will be returned as 1.
     """
     # System needs to be either a constant or an LTI system
-    if isinstance(sys, (int, float, complex)):
+    if isinstance(sys, (int, float, complex, np.number)):
         return None
     elif not isinstance(sys, LTI):
         raise ValueError("Timebase not defined")
@@ -162,7 +163,7 @@ def isdtime(sys, strict=False):
     """
 
     # Check to see if this is a constant
-    if isinstance(sys, (int, float, complex)):
+    if isinstance(sys, (int, float, complex, np.number)):
         # OK as long as strict checking is off
         return True if not strict else False
 
@@ -187,7 +188,7 @@ def isctime(sys, strict=False):
     """
 
     # Check to see if this is a constant
-    if isinstance(sys, (int, float, complex)):
+    if isinstance(sys, (int, float, complex, np.number)):
         # OK as long as strict checking is off
         return True if not strict else False
 
diff --git a/control/statesp.py b/control/statesp.py
index 13e662f03..816485f77 100644
--- a/control/statesp.py
+++ b/control/statesp.py
@@ -58,6 +58,7 @@
 from numpy.random import rand, randn
 from numpy.linalg import solve, eigvals, matrix_rank
 from numpy.linalg.linalg import LinAlgError
+import scipy as sp
 from scipy.signal import lti, cont2discrete
 # from exceptions import Exception
 import warnings
@@ -218,7 +219,7 @@ def __add__(self, other):
         """Add two LTI systems (parallel connection)."""
 
         # Check for a couple of special cases
-        if (isinstance(other, (int, float, complex))):
+        if (isinstance(other, (int, float, complex, np.number))):
             # Just adding a scalar; put it in the D matrix
             A, B, C = self.A, self.B, self.C;
             D = self.D + other;
@@ -275,7 +276,7 @@ def __mul__(self, other):
         """Multiply two LTI objects (serial connection)."""
 
         # Check for a couple of special cases
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             # Just multiplying by a scalar; change the output
             A, B = self.A, self.B
             C = self.C * other
@@ -316,7 +317,7 @@ def __rmul__(self, other):
         """Right multiply two LTI objects (serial connection)."""
 
         # Check for a couple of special cases
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             # Just multiplying by a scalar; change the input
             A, C = self.A, self.C;
             B = self.B * other;
@@ -699,11 +700,10 @@ def _convertToStateSpace(sys, **kw):
                 # TODO: do we want to squeeze first and check dimenations?
                 # I think this will fail if num and den aren't 1-D after
                 # the squeeze
-                lti_sys = lti(squeeze(sys.num), squeeze(sys.den))
-                return StateSpace(lti_sys.A, lti_sys.B, lti_sys.C, lti_sys.D,
-                                  sys.dt)
+                A, B, C, D = sp.signal.tf2ss(squeeze(sys.num), squeeze(sys.den))
+                return StateSpace(A, B, C, D, sys.dt)
 
-    elif isinstance(sys, (int, float, complex)):
+    elif isinstance(sys, (int, float, complex, np.number)):
         if "inputs" in kw:
             inputs = kw["inputs"]
         else:
diff --git a/control/xferfcn.py b/control/xferfcn.py
index be21f8509..0d7d2f417 100644
--- a/control/xferfcn.py
+++ b/control/xferfcn.py
@@ -52,10 +52,11 @@
 """
 
 # External function declarations
+import numpy as np
 from numpy import angle, any, array, empty, finfo, insert, ndarray, ones, \
     polyadd, polymul, polyval, roots, sort, sqrt, zeros, squeeze, exp, pi, \
     where, delete, real, poly, poly1d
-import numpy as np
+import scipy as sp
 from scipy.signal import lti, tf2zpk, zpk2tf, cont2discrete
 from copy import deepcopy
 from warnings import warn
@@ -126,7 +127,7 @@ def __init__(self, *args):
         data = [num, den]
         for i in range(len(data)):
             # Check for a scalar (including 0d ndarray)
-            if (isinstance(data[i], (int, float, complex)) or
+            if (isinstance(data[i], (int, float, complex, np.number)) or
                 (isinstance(data[i], ndarray) and data[i].ndim == 0)):
                 # Convert scalar to list of list of array.
                 if (isinstance(data[i], int)):
@@ -135,7 +136,7 @@ def __init__(self, *args):
                 else:
                     data[i] = [[array([data[i]])]]
             elif (isinstance(data[i], (list, tuple, ndarray)) and
-                    isinstance(data[i][0], (int, float, complex))):
+                    isinstance(data[i][0], (int, float, complex, np.number))):
                 # Convert array to list of list of array.
                 if (isinstance(data[i][0], int)):
                     # Convert integers to floats at this point
@@ -146,7 +147,8 @@ def __init__(self, *args):
             elif (isinstance(data[i], list) and
                     isinstance(data[i][0], list) and
                     isinstance(data[i][0][0], (list, tuple, ndarray)) and
-                    isinstance(data[i][0][0][0], (int, float, complex))):
+                    isinstance(data[i][0][0][0], (int, float, complex, 
+                                                  np.number))):
                 # We might already have the right format.  Convert the
                 # coefficient vectors to arrays, if necessary.
                 for j in range(len(data[i])):
@@ -363,7 +365,7 @@ def __rsub__(self, other):
     def __mul__(self, other):
         """Multiply two LTI objects (serial connection)."""
         # Convert the second argument to a transfer function.
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             other = _convertToTransferFunction(other, inputs=self.inputs,
                                                outputs=self.inputs)
         else:
@@ -410,7 +412,7 @@ def __rmul__(self, other):
         """Right multiply two LTI objects (serial connection)."""
 
         # Convert the second argument to a transfer function.
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             other = _convertToTransferFunction(other, inputs=self.inputs,
                                                outputs=self.inputs)
         else:
@@ -458,7 +460,7 @@ def __rmul__(self, other):
     def __truediv__(self, other):
         """Divide two LTI objects."""
 
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             other = _convertToTransferFunction(
                 other, inputs=self.inputs,
                 outputs=self.inputs)
@@ -492,7 +494,7 @@ def __div__(self, other):
     # TODO: Division of MIMO transfer function objects is not written yet.
     def __rtruediv__(self, other):
         """Right divide two LTI objects."""
-        if isinstance(other, (int, float, complex)):
+        if isinstance(other, (int, float, complex, np.number)):
             other = _convertToTransferFunction(
                 other, inputs=self.inputs,
                 outputs=self.inputs)
@@ -1128,22 +1130,21 @@ def _convertToTransferFunction(sys, **kw):
                         # Each transfer function matrix row
                         # has a common denominator.
                         den[i][j] = list(tfout[5][i, :])
-                # print(num)
-                # print(den)
+
             except ImportError:
                 # If slycot is not available, use signal.lti (SISO only)
                 if (sys.inputs != 1 or sys.outputs != 1):
                     raise TypeError("No support for MIMO without slycot")
 
-                lti_sys = lti(sys.A, sys.B, sys.C, sys.D)
-                num = squeeze(lti_sys.num)
-                den = squeeze(lti_sys.den)
-                # print(num)
-                # print(den)
+                # Do the conversion using sp.signal.ss2tf
+                # Note that this returns a 2D array for the numerator
+                num, den = sp.signal.ss2tf(sys.A, sys.B, sys.C, sys.D)
+                num = squeeze(num) # Convert to 1D array
+                den = squeeze(den) # Probably not needed
 
         return TransferFunction(num, den, sys.dt)
 
-    elif isinstance(sys, (int, float, complex)):
+    elif isinstance(sys, (int, float, complex, np.number)):
         if "inputs" in kw:
             inputs = kw["inputs"]
         else:

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