diff --git a/js/src/jsdbg.cpp b/js/src/jsdbg.cpp
index 717ace2781e..203f0eb7a9c 100644
--- a/js/src/jsdbg.cpp
+++ b/js/src/jsdbg.cpp
@@ -115,25 +115,39 @@ CheckThisClass(JSContext *cx, Value *vp, Class *clasp, const char *fnname)
 
 Debug::Debug(JSObject *dbg, JSObject *hooks, JSCompartment *compartment)
   : object(dbg), debuggeeCompartment(compartment), hooksObject(hooks),
-    enabled(true), hasDebuggerHandler(false)
+    uncaughtExceptionHook(NULL), enabled(true), hasDebuggerHandler(false)
 {
 }
 
 JSTrapStatus
-Debug::fireUncaughtExceptionHook(JSContext *cx)
+Debug::handleUncaughtException(AutoCompartment &ac, Value *vp, bool callHook)
 {
-    // FIXME
-    JS_ReportPendingException(cx);
-    JS_ClearPendingException(cx);
+    JSContext *cx = ac.context;
+    if (cx->isExceptionPending()) {
+        if (callHook && uncaughtExceptionHook) {
+            Value fval = ObjectValue(*uncaughtExceptionHook);
+            Value exc = cx->getPendingException();
+            Value rv;
+            cx->clearPendingException();
+            if (ExternalInvoke(cx, UndefinedValue(), fval, 1, &exc, &rv))
+                return parseResumptionValue(ac, true, rv, vp, false);
+        }
+ 
+        if (cx->isExceptionPending()) {
+            JS_ReportPendingException(cx);
+            cx->clearPendingException();
+        }
+    }
     return JSTRAP_ERROR;
 }
 
 JSTrapStatus
-Debug::parseResumptionValue(AutoCompartment &ac, bool ok, const Value &rv, Value *vp)
+Debug::parseResumptionValue(AutoCompartment &ac, bool ok, const Value &rv, Value *vp,
+                            bool callHook)
 {
     vp->setUndefined();
     if (!ok)
-        return fireUncaughtExceptionHook(ac.context);
+        return handleUncaughtException(ac, vp, callHook);
     if (rv.isUndefined())
         return JSTRAP_CONTINUE;
     if (rv.isNull())
@@ -153,18 +167,18 @@ Debug::parseResumptionValue(AutoCompartment &ac, bool ok, const Value &rv, Value
         !shape->isDataDescriptor())
     {
         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_DEBUG_BAD_RESUMPTION);
-        return fireUncaughtExceptionHook(cx);
+        return handleUncaughtException(ac, vp, callHook);
     }
 
     if (!js_NativeGet(cx, obj, obj, shape, 0, vp))
-        return fireUncaughtExceptionHook(cx);
+        return handleUncaughtException(ac, vp, callHook);
 
     // Throwing or returning objects is not yet supported. It requires
     // unwrapping.
     if (vp->isObject()) {
         vp->setUndefined();
         NotImplemented(cx);
-        return fireUncaughtExceptionHook(cx);
+        return handleUncaughtException(ac, vp, callHook);
     }
 
     ac.leave();
@@ -281,8 +295,9 @@ void
 Debug::trace(JSTracer *trc, JSObject *obj)
 {
     if (Debug *dbg = (Debug *) obj->getPrivate()) {
-        if (dbg->hooksObject)
-            MarkObject(trc, *dbg->hooksObject, "hooks");
+        MarkObject(trc, *dbg->hooksObject, "hooks");
+        if (dbg->uncaughtExceptionHook)
+            MarkObject(trc, *dbg->uncaughtExceptionHook, "hooks");
     }
 }
 
@@ -325,7 +340,7 @@ JSBool
 Debug::getHooks(JSContext *cx, uintN argc, Value *vp)
 {
     THISOBJ(cx, vp, Debug, "get hooks", thisobj, dbg);
-    vp->setObjectOrNull(dbg->hooksObject);
+    vp->setObject(*dbg->hooksObject);
     return true;
 }
 
@@ -366,6 +381,26 @@ Debug::setEnabled(JSContext *cx, uintN argc, Value *vp)
     return true;
 }
 
+JSBool
+Debug::getUncaughtExceptionHook(JSContext *cx, uintN argc, Value *vp)
+{
+    THISOBJ(cx, vp, Debug, "get uncaughtExceptionHook", thisobj, dbg);
+    vp->setObjectOrNull(dbg->uncaughtExceptionHook);
+    return true;
+}
+
+JSBool
+Debug::setUncaughtExceptionHook(JSContext *cx, uintN argc, Value *vp)
+{
+    REQUIRE_ARGC("Debug.set uncaughtExceptionHook", 1);
+    THISOBJ(cx, vp, Debug, "set uncaughtExceptionHook", thisobj, dbg);
+    if (!vp[2].isObjectOrNull())
+        return ReportObjectRequired(cx);
+    dbg->uncaughtExceptionHook = vp[2].toObjectOrNull();
+    vp->setUndefined();
+    return true;
+}
+
 JSBool
 Debug::construct(JSContext *cx, uintN argc, Value *vp)
 {
@@ -415,6 +450,8 @@ Debug::construct(JSContext *cx, uintN argc, Value *vp)
 JSPropertySpec Debug::properties[] = {
     JS_PSGS("hooks", Debug::getHooks, Debug::setHooks, 0),
     JS_PSGS("enabled", Debug::getEnabled, Debug::setEnabled, 0),
+    JS_PSGS("uncaughtExceptionHook", Debug::getUncaughtExceptionHook,
+            Debug::setUncaughtExceptionHook, 0),
     JS_PS_END
 };
     
diff --git a/js/src/jsdbg.h b/js/src/jsdbg.h
index 267d2d476c8..57533f2b628 100644
--- a/js/src/jsdbg.h
+++ b/js/src/jsdbg.h
@@ -56,15 +56,16 @@ class Debug {
     JSObject *object;  // The Debug object. Strong reference.
     JSCompartment *debuggeeCompartment;  // Weak reference.
     JSObject *hooksObject;  // See Debug.prototype.hooks. Strong reference.
-
+    JSObject *uncaughtExceptionHook;  // Strong reference.
     bool enabled;
 
     // True if hooksObject had a debuggerHandler property when the hooks
     // property was set.
     bool hasDebuggerHandler;
 
-    JSTrapStatus fireUncaughtExceptionHook(JSContext *cx);
-    JSTrapStatus parseResumptionValue(AutoCompartment &ac, bool ok, const Value &rv, Value *vp);
+    JSTrapStatus handleUncaughtException(AutoCompartment &ac, Value *vp, bool callHook);
+    JSTrapStatus parseResumptionValue(AutoCompartment &ac, bool ok, const Value &rv, Value *vp,
+                                      bool callHook = true);
 
     static void trace(JSTracer *trc, JSObject *obj);
     static void finalize(JSContext *cx, JSObject *obj);
@@ -74,6 +75,8 @@ class Debug {
     static JSBool setHooks(JSContext *cx, uintN argc, Value *vp);
     static JSBool getEnabled(JSContext *cx, uintN argc, Value *vp);
     static JSBool setEnabled(JSContext *cx, uintN argc, Value *vp);
+    static JSBool getUncaughtExceptionHook(JSContext *cx, uintN argc, Value *vp);
+    static JSBool setUncaughtExceptionHook(JSContext *cx, uintN argc, Value *vp);
     static JSBool construct(JSContext *cx, uintN argc, Value *vp);
     static JSPropertySpec properties[];
 
diff --git a/js/src/tests/js1_8_5/extensions/debug-object-18.js b/js/src/tests/js1_8_5/extensions/debug-object-18.js
new file mode 100644
index 00000000000..abbdaece102
--- /dev/null
+++ b/js/src/tests/js1_8_5/extensions/debug-object-18.js
@@ -0,0 +1,25 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+// Uncaught exceptions in the debugger itself are delivered to the
+// uncaughtExceptionHook.
+
+var g = newGlobal('new-compartment');
+var dbg = new Debug(g);
+var log;
+dbg.hooks = {
+    debuggerHandler: function () {
+        log += 'x';
+        throw new TypeError("fail");
+    }
+};
+dbg.uncaughtExceptionHook = function (exc) {
+    assertEq(exc instanceof TypeError, true);
+    log += '!';
+};
+
+log = '';
+g.eval("debugger");
+assertEq(log, 'x!');
+
+reportCompare(0, 0, 'ok');
diff --git a/js/src/tests/js1_8_5/extensions/debug-object-19.js b/js/src/tests/js1_8_5/extensions/debug-object-19.js
new file mode 100644
index 00000000000..94fe0703bd3
--- /dev/null
+++ b/js/src/tests/js1_8_5/extensions/debug-object-19.js
@@ -0,0 +1,34 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+// uncaughtExceptionHook returns a resumption value.
+
+var g = newGlobal('new-compartment');
+var dbg = new Debug(g);
+var rv;
+dbg.hooks = {debuggerHandler: function () { throw 15; }};
+dbg.uncaughtExceptionHook = function (exc) {
+    assertEq(exc, 15);
+    return rv;
+};
+
+// case 1: undefined
+rv = undefined;
+g.eval("debugger");
+
+// case 2: throw
+rv = {throw: 57};
+var result;
+try {
+    g.eval("debugger");
+    result = 'no exception thrown';
+} catch (exc) {
+    result = 'caught ' + exc;
+}
+assertEq(result, 'caught 57');
+
+// case 3: return
+rv = {return: 42};
+assertEq(g.eval("debugger;"), 42);
+
+reportCompare(0, 0, 'ok');
diff --git a/js/src/tests/js1_8_5/extensions/debug-object-20.js b/js/src/tests/js1_8_5/extensions/debug-object-20.js
new file mode 100644
index 00000000000..939bb0a0ba8
--- /dev/null
+++ b/js/src/tests/js1_8_5/extensions/debug-object-20.js
@@ -0,0 +1,32 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/licenses/publicdomain/
+
+// uncaughtExceptionHook resumption value other than undefined causes further
+// hooks to be skipped.
+
+var g = newGlobal('new-compartment');
+var log;
+
+function makeDebug(g, name) {
+    var dbg = new Debug(g);
+    dbg.hooks = {
+        debuggerHandler: function () {
+            log += name;
+            throw new Error(name);
+        }
+    };
+    dbg.uncaughtExceptionHook = function (exc) {
+        assertEq(exc.message, name);
+        return name == "2" ? {return: 42} : undefined;
+    };
+}
+
+var arr = [];
+for (var i = 0; i < 6; i++)
+    arr[i] = makeDebug(g, "" + i);
+
+log = '';
+assertEq(g.eval("debugger;"), 42);
+assertEq(log, "012");
+
+reportCompare(0, 0, 'ok');
diff --git a/js/src/tests/js1_8_5/extensions/jstests.list b/js/src/tests/js1_8_5/extensions/jstests.list
index 0ea54c1165a..50c169f78bb 100644
--- a/js/src/tests/js1_8_5/extensions/jstests.list
+++ b/js/src/tests/js1_8_5/extensions/jstests.list
@@ -58,3 +58,6 @@ skip-if(!xulRuntime.shell) script debug-object-14.js
 skip-if(!xulRuntime.shell) script debug-object-15.js
 skip-if(!xulRuntime.shell) script debug-object-16.js
 skip-if(!xulRuntime.shell) script debug-object-17.js
+skip-if(!xulRuntime.shell) script debug-object-18.js
+skip-if(!xulRuntime.shell) script debug-object-19.js
+skip-if(!xulRuntime.shell) script debug-object-20.js