--- a/layout/style/nsCSSParser.cpp
+++ b/layout/style/nsCSSParser.cpp
@@ -6427,17 +6427,17 @@ CSSParserImpl::ParseDeclarationBlock(uin
       REPORT_UNEXPECTED_TOKEN(PEBadDeclBlockStart);
       OUTPUT_ERROR();
       return nullptr;
     }
   }
   RefPtr<css::Declaration> declaration = new css::Declaration();
   mData.AssertInitialState();
   for (;;) {
-    bool changed;
+    bool changed = false;
     if (!ParseDeclaration(declaration, aFlags, true, &changed, aContext)) {
       if (!SkipDeclaration(checkForBraces)) {
         break;
       }
       if (checkForBraces) {
         if (ExpectSymbol('}', true)) {
           break;
         }