diff --git a/stepmania/src/RageSoundReader_MP3.cpp b/stepmania/src/RageSoundReader_MP3.cpp
index 053fd9e9a4..0006a8e0d4 100644
--- a/stepmania/src/RageSoundReader_MP3.cpp
+++ b/stepmania/src/RageSoundReader_MP3.cpp
@@ -560,6 +560,7 @@ SoundReader_FileReader::OpenResult RageSoundReader_MP3::Open( CString filename_
 {
 	filename = filename_;
     rw = fopen(filename, "rb");
+	ASSERT( rw );
 
 	mad_frame_mute( &mad->Frame );
 	mad_timer_reset( &mad->Timer );