diff --git a/src/lib/xiph/FlacStreamMetadata.cxx b/src/lib/xiph/FlacStreamMetadata.cxx
index cdd7ef99c..6121764fc 100644
--- a/src/lib/xiph/FlacStreamMetadata.cxx
+++ b/src/lib/xiph/FlacStreamMetadata.cxx
@@ -32,6 +32,8 @@
 #include "ReplayGainInfo.hxx"
 #include "util/DivideString.hxx"
 
+#include <assert.h>
+
 bool
 flac_parse_replay_gain(ReplayGainInfo &rgi,
 		       const FLAC__StreamMetadata_VorbisComment &vc)