--- a/media/gmp-clearkey/0.1/ClearKeyUtils.cpp
+++ b/media/gmp-clearkey/0.1/ClearKeyUtils.cpp
@@ -231,16 +231,19 @@ static bool SkipToken(ParserContext& aCt
 
 static bool
 SkipString(ParserContext& aCtx)
 {
   EXPECT_SYMBOL(aCtx, '"');
   for (uint8_t sym = GetNextSymbol(aCtx); sym; sym = GetNextSymbol(aCtx)) {
     if (sym == '\\') {
       sym = GetNextSymbol(aCtx);
+      if (!sym) {
+          return false;
+      }
     } else if (sym == '"') {
       return true;
     }
   }
 
   return false;
 }