diff --git a/dom/indexedDB/IDBFactory.cpp b/dom/indexedDB/IDBFactory.cpp
index 4e91d29f23f..667b5cddc3b 100644
--- a/dom/indexedDB/IDBFactory.cpp
+++ b/dom/indexedDB/IDBFactory.cpp
@@ -59,7 +59,7 @@
 #include "IDBKeyRange.h"
 #include "LazyIdleThread.h"
 
-#define DB_SCHEMA_VERSION 1
+#define DB_SCHEMA_VERSION 2
 
 USING_INDEXEDDB_NAMESPACE
 
@@ -155,7 +155,7 @@ CreateTables(mozIStorageConnection* aDBConn)
   NS_ENSURE_SUCCESS(rv, rv);
 
   rv = aDBConn->ExecuteSimpleSQL(NS_LITERAL_CSTRING(
-    "CREATE INDEX key_index "
+    "CREATE UNIQUE INDEX key_index "
     "ON object_data (key_value, object_store_id);"
   ));
   NS_ENSURE_SUCCESS(rv, rv);
@@ -174,7 +174,7 @@ CreateTables(mozIStorageConnection* aDBConn)
   NS_ENSURE_SUCCESS(rv, rv);
 
   rv = aDBConn->ExecuteSimpleSQL(NS_LITERAL_CSTRING(
-    "CREATE INDEX ai_key_index "
+    "CREATE UNIQUE INDEX ai_key_index "
     "ON ai_object_data (id, object_store_id);"
   ));
   NS_ENSURE_SUCCESS(rv, rv);
diff --git a/dom/indexedDB/IDBObjectStore.cpp b/dom/indexedDB/IDBObjectStore.cpp
index 8d50dc03c10..7ebb79aeaa8 100644
--- a/dom/indexedDB/IDBObjectStore.cpp
+++ b/dom/indexedDB/IDBObjectStore.cpp
@@ -1369,8 +1369,43 @@ AddHelper::DoDatabaseWork(mozIStorageConnection* aConnection)
   rv = stmt->BindStringByName(NS_LITERAL_CSTRING("data"), mValue);
   NS_ENSURE_SUCCESS(rv, nsIIDBDatabaseException::UNKNOWN_ERR);
 
-  if (NS_FAILED(stmt->Execute())) {
-    return nsIIDBDatabaseException::CONSTRAINT_ERR;
+  rv = stmt->Execute();
+  if (NS_FAILED(rv)) {
+    if (mCreate && mayOverwrite && rv == NS_ERROR_STORAGE_CONSTRAINT) {
+      scoper.Abandon();
+
+      stmt = mTransaction->AddStatement(false, true, mAutoIncrement);
+      NS_ENSURE_TRUE(stmt, nsIIDBDatabaseException::UNKNOWN_ERR);
+
+      mozStorageStatementScoper scoper2(stmt);
+
+      rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("osid"), mOSID);
+      NS_ENSURE_SUCCESS(rv, nsIIDBDatabaseException::UNKNOWN_ERR);
+
+      if (!mAutoIncrement) {
+        NS_ASSERTION(!mKey.IsUnset(), "This shouldn't happen!");
+
+        if (mKey.IsInt()) {
+          rv = stmt->BindInt64ByName(keyValue, mKey.IntValue());
+        }
+        else if (mKey.IsString()) {
+          rv = stmt->BindStringByName(keyValue, mKey.StringValue());
+        }
+        else {
+          NS_NOTREACHED("Unknown key type!");
+        }
+        NS_ENSURE_SUCCESS(rv, nsIIDBDatabaseException::UNKNOWN_ERR);
+      }
+
+      rv = stmt->BindStringByName(NS_LITERAL_CSTRING("data"), mValue);
+      NS_ENSURE_SUCCESS(rv, nsIIDBDatabaseException::UNKNOWN_ERR);
+
+      rv = stmt->Execute();
+    }
+
+    if (NS_FAILED(rv)) {
+      return nsIIDBDatabaseException::CONSTRAINT_ERR;
+    }
   }
 
   // If we are supposed to generate a key, get the new id.
@@ -1777,10 +1812,9 @@ OpenCursorHelper::GetSuccessResult(nsIWritableVariant* aResult)
     IDBCursor::Create(mRequest, mTransaction, mObjectStore, mDirection, mData);
   NS_ENSURE_TRUE(cursor, nsIIDBDatabaseException::UNKNOWN_ERR);
 
-  aResult->SetAsISupports(static_cast<IDBRequest::Generator*>(cursor));
-
   mObjectStore = nsnull;
 
+  aResult->SetAsISupports(static_cast<IDBRequest::Generator*>(cursor));
   return OK;
 }
 
@@ -1961,6 +1995,8 @@ CreateIndexHelper::GetSuccessResult(nsIWritableVariant* aResult)
   nsresult rv = mObjectStore->Index(mName, getter_AddRefs(result));
   NS_ENSURE_SUCCESS(rv, nsIIDBDatabaseException::UNKNOWN_ERR);
 
+  mObjectStore = nsnull;
+
   aResult->SetAsISupports(result);
   return OK;
 }
@@ -2022,6 +2058,7 @@ RemoveIndexHelper::GetSuccessResult(nsIWritableVariant* /* aResult */)
     }
   }
 
+  mObjectStore = nsnull;
   return OK;
 }
 
diff --git a/dom/indexedDB/IDBTransaction.cpp b/dom/indexedDB/IDBTransaction.cpp
index 5b278408e1a..ac75299ac81 100644
--- a/dom/indexedDB/IDBTransaction.cpp
+++ b/dom/indexedDB/IDBTransaction.cpp
@@ -264,7 +264,7 @@ IDBTransaction::AddStatement(bool aCreate,
     if (aCreate) {
       if (aOverwrite) {
         return GetCachedStatement(
-          "INSERT OR REPLACE INTO ai_object_data (object_store_id, id, data) "
+          "INSERT OR FAIL INTO ai_object_data (object_store_id, id, data) "
           "VALUES (:osid, :key_value, :data)"
         );
       }
@@ -283,7 +283,7 @@ IDBTransaction::AddStatement(bool aCreate,
   if (aCreate) {
     if (aOverwrite) {
       return GetCachedStatement(
-        "INSERT OR REPLACE INTO object_data (object_store_id, key_value, data) "
+        "INSERT OR FAIL INTO object_data (object_store_id, key_value, data) "
         "VALUES (:osid, :key_value, :data)"
       );
     }