diff --git a/mozilla/extensions/java/xpcom/Makefile.in b/mozilla/extensions/java/xpcom/Makefile.in
index c4792030524..d03a0ba5127 100644
--- a/mozilla/extensions/java/xpcom/Makefile.in
+++ b/mozilla/extensions/java/xpcom/Makefile.in
@@ -65,6 +65,7 @@ CPPSRCS		= \
 # Can't use JAVA_SRCS for now, since that one is referenced in config.mk
 JAVA_SRCS_ = \
 		XPCOM.java \
+		XPCOMException.java \
 		GeckoEmbed.java \
 		$(NULL)
 
@@ -100,7 +101,7 @@ _IGNORE_STUBS = domstubs gfxIFormats
 IGNORE_STUBS = $(patsubst %,org/mozilla/xpcom/stubs/%_Stub.class,$(_IGNORE_STUBS))
 JAVA_STUB_CLASSES = $(filter-out $(IGNORE_STUBS),$(_JAVA_STUB_CLASSES))
 
-GARBAGE = $(EMBED_JAR) $(EMBED_JAR_SRC)
+GARBAGE += $(EMBED_JAR) $(EMBED_JAR_SRC)
 GARBAGE_DIRS += $(XPIDL_GEN_DIR) org
 
 include $(topsrcdir)/config/rules.mk
diff --git a/mozilla/extensions/java/xpcom/XPCOMException.java b/mozilla/extensions/java/xpcom/XPCOMException.java
new file mode 100644
index 00000000000..7c597bdd2d8
--- /dev/null
+++ b/mozilla/extensions/java/xpcom/XPCOMException.java
@@ -0,0 +1,58 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (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.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Java XPCOM Bindings.
+ *
+ * The Initial Developer of the Original Code is
+ * IBM Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 2004
+ * IBM Corporation. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Javier Pedemonte (jhpedemonte@gmail.com)
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+package org.mozilla.xpcom;
+
+public final class XPCOMException extends RuntimeException {
+
+  public XPCOMException() {
+    super();
+  }
+
+  public XPCOMException(String message) {
+    super(message);
+  }
+
+  public XPCOMException(String message, Throwable cause) {
+    super(message, cause);
+  }
+
+  public XPCOMException(Throwable cause) {
+    super(cause);
+  }
+}
+
diff --git a/mozilla/extensions/java/xpcom/nsJavaXPCOMBindingUtils.cpp b/mozilla/extensions/java/xpcom/nsJavaXPCOMBindingUtils.cpp
index 77f8e082678..4ae436e7b90 100644
--- a/mozilla/extensions/java/xpcom/nsJavaXPCOMBindingUtils.cpp
+++ b/mozilla/extensions/java/xpcom/nsJavaXPCOMBindingUtils.cpp
@@ -100,7 +100,7 @@ jclass stringArrayClass = nsnull;
 
 jclass nsISupportsClass = nsnull;
 
-jclass exceptionClass = nsnull;
+jclass xpcomExceptionClass = nsnull;
 
 /**************************************
  *  Java<->XPCOM binding stores
@@ -342,8 +342,8 @@ InitializeJavaGlobals(JNIEnv *env)
         return PR_FALSE;
     }
   
-    if (!(clazz = env->FindClass("java/lang/Exception")) ||
-        !(exceptionClass = (jclass) env->NewGlobalRef(clazz)))
+    if (!(clazz = env->FindClass("org/mozilla/xpcom/XPCOMException")) ||
+        !(xpcomExceptionClass = (jclass) env->NewGlobalRef(clazz)))
     {
         return PR_FALSE;
     }
@@ -518,12 +518,14 @@ CreateJavaXPCOMInstance(nsISupports* aXPCOMObject, const nsIID* aIID)
 void
 ThrowXPCOMException(JNIEnv* env, int aFailureCode)
 {
-  // only throw this exception if one hasn't already been thrown
+  // Only throw this exception if one hasn't already been thrown, so we don't
+  // mask a previous exception/error.
   jthrowable throwObj = env->ExceptionOccurred();
-  if (throwObj != nsnull) {
-    char exp_msg[32];
-    sprintf(exp_msg, "\nInternal Gecko Error: %x", aFailureCode);
-    env->ThrowNew(exceptionClass, exp_msg);
+  if (throwObj == nsnull) {
+    char exp_msg[40];
+    sprintf(exp_msg, "\nInternal XPCOM Error: %x", aFailureCode);
+    jint rc = env->ThrowNew(xpcomExceptionClass, exp_msg);
+    NS_ASSERTION(rc == 0, "Failed to throw XPCOMException");
   }
 }