diff --git a/src/com/google/javascript/jscomp/RuntimeTypeCheck.java b/src/com/google/javascript/jscomp/RuntimeTypeCheck.java
index 73454daca7a..8436bbc9b8b 100644
--- a/src/com/google/javascript/jscomp/RuntimeTypeCheck.java
+++ b/src/com/google/javascript/jscomp/RuntimeTypeCheck.java
@@ -16,6 +16,9 @@
 
 package com.google.javascript.jscomp;
 
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.javascript.rhino.IR;
@@ -371,19 +374,27 @@ private Node createCheckerNode(JSType type) {
 
   private void addBoilerplateCode() {
     Node newNode = compiler.ensureLibraryInjected("runtime_type_check", false);
-    if (newNode != null && logFunction != null) {
-      // Inject the custom log function.
-      Node logOverride = IR.exprResult(
-          IR.assign(
-              NodeUtil.newQName(
-                  compiler,
-                  "$jscomp.typecheck.log"),
-              NodeUtil.newQName(
-                  compiler,
-                  logFunction)));
-      newNode.getParent().addChildAfter(logOverride, newNode);
-      compiler.reportChangeToEnclosingScope(newNode);
+    if (newNode != null) {
+      injectCustomLogFunction(newNode);
+    }
+  }
+
+  @VisibleForTesting
+  void injectCustomLogFunction(Node node) {
+    if (logFunction == null) {
+      return;
     }
+    checkState(
+        NodeUtil.isValidQualifiedName(compiler.getFeatureSet(), logFunction),
+        "%s is not a valid qualified name", logFunction);
+    Node logOverride =
+        IR.exprResult(
+            IR.assign(
+                NodeUtil.newQName(compiler, "$jscomp.typecheck.log"),
+                NodeUtil.newQName(compiler, logFunction)));
+    checkState(node.getParent().isScript(), node.getParent());
+    node.getParent().addChildAfter(logOverride, node);
+    compiler.reportChangeToEnclosingScope(node);
   }
 
   private Node jsCode(String prop) {
diff --git a/test/com/google/javascript/jscomp/RuntimeTypeCheckTest.java b/test/com/google/javascript/jscomp/RuntimeTypeCheckTest.java
index e5713de3774..c061b5a60b7 100644
--- a/test/com/google/javascript/jscomp/RuntimeTypeCheckTest.java
+++ b/test/com/google/javascript/jscomp/RuntimeTypeCheckTest.java
@@ -18,11 +18,16 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
+import com.google.javascript.rhino.IR;
+import com.google.javascript.rhino.Node;
+import javax.annotation.Nullable;
+
 /**
  * Tests for {@link RuntimeTypeCheck}.
  *
  */
 public final class RuntimeTypeCheckTest extends CompilerTestCase {
+  @Nullable private String logFunction = null;
 
   public RuntimeTypeCheckTest() {
     super("/** @const */ var undefined;");
@@ -313,6 +318,40 @@ public void testFunctionType() {
     testChecksSame("/** @type {!Function} */function f() {}");
   }
 
+  public void testInjectLogFunction_name() {
+    logFunction = "myLogFn";
+    Compiler compiler = createCompiler();
+    compiler.initOptions(getOptions());
+    Node testNode = IR.exprResult(IR.nullNode());
+    IR.script(testNode);
+    getProcessor(compiler).injectCustomLogFunction(testNode);
+    assertThat(compiler.toSource(testNode.getParent())).contains("$jscomp.typecheck.log=myLogFn");
+  }
+
+  public void testInjectLogFunction_qualifiedName() {
+    logFunction = "my.log.fn";
+    Compiler compiler = createCompiler();
+    compiler.initOptions(getOptions());
+    Node testNode = IR.exprResult(IR.nullNode());
+    IR.script(testNode);
+    getProcessor(compiler).injectCustomLogFunction(testNode);
+    assertThat(compiler.toSource(testNode.getParent())).contains("$jscomp.typecheck.log=my.log.fn");
+  }
+
+  public void testInvalidLogFunction() {
+    logFunction = "{}"; // Not a valid qualified name
+    Compiler compiler = createCompiler();
+    compiler.initOptions(getOptions());
+    Node testNode = IR.exprResult(IR.nullNode());
+    IR.script(testNode);
+    try {
+      getProcessor(compiler).injectCustomLogFunction(testNode);
+      fail("Expected an IllegalStateException");
+    } catch (IllegalStateException e) {
+      assertThat(e).hasMessageThat().contains("not a valid qualified name");
+    }
+  }
+
   private void testChecks(String js, String expected) {
     test(js, expected);
     assertThat(getLastCompiler().injected).containsExactly("runtime_type_check");
@@ -334,8 +373,8 @@ protected NoninjectingCompiler getLastCompiler() {
   }
 
   @Override
-  protected CompilerPass getProcessor(final Compiler compiler) {
-    return new RuntimeTypeCheck(compiler, null);
+  protected RuntimeTypeCheck getProcessor(final Compiler compiler) {
+    return new RuntimeTypeCheck(compiler, logFunction);
   }
 
   @Override