diff --git a/xpcom/ds/nsAtomTable.cpp b/xpcom/ds/nsAtomTable.cpp
index b2b21ee34ec..441c41b451b 100644
--- a/xpcom/ds/nsAtomTable.cpp
+++ b/xpcom/ds/nsAtomTable.cpp
@@ -107,7 +107,15 @@ AtomTableGetHash(PLDHashTable *table, const void *key)
   const AtomTableKey *k = static_cast<const AtomTableKey*>(key);
 
   if (k->mUTF8String) {
-    return nsCRT::HashCodeAsUTF16(k->mUTF8String, k->mLength);;
+    PRBool err;
+    PRUint32 hash = nsCRT::HashCodeAsUTF16(k->mUTF8String, k->mLength, &err);
+    if (err) {
+      AtomTableKey* mutableKey = const_cast<AtomTableKey*>(k);
+      mutableKey->mUTF8String = nsnull;
+      mutableKey->mLength = 0;
+      hash = 0;
+    }
+    return hash;
   }
 
   return nsCRT::HashCode(k->mUTF16String, k->mLength);
diff --git a/xpcom/ds/nsCRT.cpp b/xpcom/ds/nsCRT.cpp
index 06ac61c33d2..ca1f49997b5 100644
--- a/xpcom/ds/nsCRT.cpp
+++ b/xpcom/ds/nsCRT.cpp
@@ -253,17 +253,19 @@ PRUint32 nsCRT::HashCode(const PRUnichar* start, PRUint32 length)
   return h;
 }
 
-PRUint32 nsCRT::HashCodeAsUTF16(const char* start, PRUint32 length)
+PRUint32 nsCRT::HashCodeAsUTF16(const char* start, PRUint32 length,
+                                PRBool* err)
 {
   PRUint32 h = 0;
   const char* s = start;
   const char* end = start + length;
 
+  *err = PR_FALSE;
+
   while ( s < end )
     {
-      PRBool err;
-      PRUint32 ucs4 = UTF8CharEnumerator::NextChar(&s, end, &err);
-      if (err) {
+      PRUint32 ucs4 = UTF8CharEnumerator::NextChar(&s, end, err);
+      if (*err) {
 	return 0;
       }
 
diff --git a/xpcom/ds/nsCRT.h b/xpcom/ds/nsCRT.h
index 8901130adff..9096b702485 100644
--- a/xpcom/ds/nsCRT.h
+++ b/xpcom/ds/nsCRT.h
@@ -242,7 +242,8 @@ public:
   // Computes a hashcode for a length number of UTF8
   // characters. Returns the same hash code as the HashCode method
   // taking a |PRUnichar*| would if the string were converted to UTF16.
-  static PRUint32 HashCodeAsUTF16(const char* start, PRUint32 length);
+  static PRUint32 HashCodeAsUTF16(const char* start, PRUint32 length,
+                                  PRBool* err);
 
   // String to longlong
   static PRInt64 atoll(const char *str);
diff --git a/xpcom/tests/TestUTF.cpp b/xpcom/tests/TestUTF.cpp
index 8dfbbb53595..01d45d4bbc5 100644
--- a/xpcom/tests/TestUTF.cpp
+++ b/xpcom/tests/TestUTF.cpp
@@ -145,21 +145,27 @@ test_hashas16()
 {
   for (unsigned int i = 0; i < NS_ARRAY_LENGTH(ValidStrings); ++i) {
     nsDependentCString str8(ValidStrings[i].m8);
+    PRBool err;
     if (nsCRT::HashCode(ValidStrings[i].m16) !=
-        nsCRT::HashCodeAsUTF16(str8.get(), str8.Length()))
+        nsCRT::HashCodeAsUTF16(str8.get(), str8.Length(), &err) ||
+        err)
       return PR_FALSE;
   }
 
   for (unsigned int i = 0; i < NS_ARRAY_LENGTH(Invalid8Strings); ++i) {
     nsDependentCString str8(Invalid8Strings[i].m8);
+    PRBool err;
     if (nsCRT::HashCode(Invalid8Strings[i].m16) !=
-        nsCRT::HashCodeAsUTF16(str8.get(), str8.Length()))
+        nsCRT::HashCodeAsUTF16(str8.get(), str8.Length(), &err) ||
+        err)
       return PR_FALSE;
   }
 
   for (unsigned int i = 0; i < NS_ARRAY_LENGTH(Malformed8Strings); ++i) {
     nsDependentCString str8(Malformed8Strings[i]);
-    if (nsCRT::HashCodeAsUTF16(str8.get(), str8.Length()) != 0)
+    PRBool err;
+    if (nsCRT::HashCodeAsUTF16(str8.get(), str8.Length(), &err) != 0 ||
+        !err)
       return PR_FALSE;
   }