--- a/dom/media/MediaDecoder.cpp
+++ b/dom/media/MediaDecoder.cpp
@@ -50,18 +50,17 @@ namespace mozilla {
 // avoid redefined macro in unified build
 #undef LOG
 #undef DUMP
 
 LazyLogModule gMediaDecoderLog("MediaDecoder");
 #define LOG(x, ...) \
   MOZ_LOG(gMediaDecoderLog, LogLevel::Debug, ("Decoder=%p " x, this, ##__VA_ARGS__))
 
-#define DUMP(x, ...) \
-  printf_stderr("%s\n", nsPrintfCString("Decoder=%p " x, this, ##__VA_ARGS__).get())
+#define DUMP(x, ...) printf_stderr(x "\n", ##__VA_ARGS__)
 
 #define NS_DispatchToMainThread(...) CompileError_UseAbstractMainThreadInstead
 
 static const char*
 ToPlayStateStr(MediaDecoder::PlayState aState)
 {
   switch (aState) {
     case MediaDecoder::PLAY_STATE_START:    return "START";