diff --git a/luni/src/main/java/java/lang/AssertionError.java b/luni/src/main/java/java/lang/AssertionError.java
index 3d0d2a484..077e57c7b 100644
--- a/luni/src/main/java/java/lang/AssertionError.java
+++ b/luni/src/main/java/java/lang/AssertionError.java
@@ -52,8 +52,10 @@ public AssertionError(String detailMessage, Throwable cause) {
      *            optionally the cause.
      */
     public AssertionError(Object detailMessage) {
-        super(String.valueOf(detailMessage),
-                (detailMessage instanceof Throwable ? (Throwable) detailMessage : null));
+        super(String.valueOf(detailMessage));
+        if (detailMessage instanceof Throwable) {
+            initCause((Throwable) detailMessage);
+        }
     }
 
     /**
diff --git a/luni/src/test/java/libcore/java/lang/AssertionErrorTest.java b/luni/src/test/java/libcore/java/lang/AssertionErrorTest.java
new file mode 100644
index 000000000..638b15b1e
--- /dev/null
+++ b/luni/src/test/java/libcore/java/lang/AssertionErrorTest.java
@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package libcore.java.lang;
+
+import junit.framework.TestCase;
+
+public final class AssertionErrorTest extends TestCase {
+    // http://code.google.com/p/android/issues/detail?id=29378
+    public void test_29378() throws Exception {
+        AssertionError ae = new AssertionError("hello");
+        ae.initCause(new Throwable());
+    }
+}