diff --git a/packages/cargo-pgml-components/Cargo.lock b/packages/cargo-pgml-components/Cargo.lock
index 89f1b1467..92f4118dc 100644
--- a/packages/cargo-pgml-components/Cargo.lock
+++ b/packages/cargo-pgml-components/Cargo.lock
@@ -126,7 +126,7 @@ dependencies = [
 
 [[package]]
 name = "cargo-pgml-components"
-version = "0.1.19"
+version = "0.1.20"
 dependencies = [
  "anyhow",
  "assert_cmd",
@@ -143,6 +143,7 @@ dependencies = [
  "regex",
  "sailfish",
  "serde",
+ "serde_json",
  "toml",
 ]
 
@@ -428,6 +429,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itoa"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af150ab688ff2122fcef229be89cb50dd66af9e01a4ff320cc137eecc9bacc38"
+
 [[package]]
 name = "itoap"
 version = "1.0.1"
@@ -670,6 +677,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "serde_json"
+version = "1.0.107"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6b420ce6e3d8bd882e9b243c6eed35dbc9a6110c9769e74b584e0d68d1f20c65"
+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "serde_spanned"
 version = "0.6.3"
diff --git a/packages/cargo-pgml-components/Cargo.toml b/packages/cargo-pgml-components/Cargo.toml
index 9638e05a2..55fff6533 100644
--- a/packages/cargo-pgml-components/Cargo.toml
+++ b/packages/cargo-pgml-components/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "cargo-pgml-components"
-version = "0.1.19"
+version = "0.1.20"
 edition = "2021"
 authors = ["PostgresML <team@postgresml.org>"]
 license = "MIT"
@@ -22,6 +22,7 @@ regex = "1"
 toml = "0.7"
 serde = { version = "1", features = ["derive"] }
 file-lock = "2"
+serde_json = "1"
 
 [dev-dependencies]
 assert_cmd = "2"
diff --git a/packages/cargo-pgml-components/src/frontend/javascript.rs b/packages/cargo-pgml-components/src/frontend/javascript.rs
index 8784d2a98..5b00a9e11 100644
--- a/packages/cargo-pgml-components/src/frontend/javascript.rs
+++ b/packages/cargo-pgml-components/src/frontend/javascript.rs
@@ -1,13 +1,14 @@
 //! Javascript bundling.
 
 use glob::glob;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::fs::{copy, read_to_string, remove_file, File};
 use std::io::Write;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::{exit, Command};
 
 use convert_case::{Case, Casing};
+use serde::{Deserialize, Serialize};
 
 use crate::config::Config;
 use crate::frontend::tools::execute_with_nvm;
@@ -32,6 +33,11 @@ static OLD_BUNLDES_GLOB: &'static str = "static/js/*.*.js";
 /// JS compiler
 static JS_COMPILER: &'static str = "rollup";
 
+#[derive(Serialize, Deserialize, Debug)]
+struct Packages {
+    dependencies: HashMap<String, String>,
+}
+
 /// Delete old bundles we may have created.
 fn cleanup_old_bundles() {
     // Clean up old bundles
@@ -146,6 +152,16 @@ pub fn bundle(config: Config, minify: bool) {
     cleanup_old_bundles();
     assemble_modules(config.clone());
 
+    let package_json = Path::new("package.json");
+
+    let packages: Packages = if package_json.is_file() {
+        let packages = unwrap_or_exit!(read_to_string(package_json));
+        unwrap_or_exit!(serde_json::from_str(&packages))
+    } else {
+        warn("package.json not found, can't validate rollup output");
+        serde_json::from_str(r#"{"dependencies": {}}"#).unwrap()
+    };
+
     let mut command = Command::new(JS_COMPILER);
 
     command
@@ -163,7 +179,17 @@ pub fn bundle(config: Config, minify: bool) {
 
     // Bundle JavaScript.
     info("bundling javascript with rollup");
-    unwrap_or_exit!(execute_with_nvm(&mut command));
+    let output = unwrap_or_exit!(execute_with_nvm(&mut command));
+
+    let lines = output.split("\n");
+    for line in lines {
+        for (package, _version) in &packages.dependencies {
+            if line.contains(package) {
+                error(&format!("unresolved import: {}", package));
+                exit(1);
+            }
+        }
+    }
 
     info(&format!("written {}", JS_FILE));
 
diff --git a/packages/cargo-pgml-components/src/util.rs b/packages/cargo-pgml-components/src/util.rs
index b2f8c4e82..fcf31ad49 100644
--- a/packages/cargo-pgml-components/src/util.rs
+++ b/packages/cargo-pgml-components/src/util.rs
@@ -69,7 +69,7 @@ pub fn execute_command(command: &mut Command) -> std::io::Result<String> {
         info!("{}", stdout);
     }
 
-    Ok(stdout)
+    Ok(stdout.clone() + &stderr)
 }
 
 pub fn write_to_file(path: &Path, content: &str) -> std::io::Result<()> {

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