diff --git a/src/tag/RiffFormat.hxx b/src/tag/RiffFormat.hxx
index f218f3529..d0d92d078 100644
--- a/src/tag/RiffFormat.hxx
+++ b/src/tag/RiffFormat.hxx
@@ -28,9 +28,13 @@ struct RiffFileHeader {
 	char format[4];
 };
 
+static_assert(sizeof(RiffFileHeader) == 12);
+
 struct RiffChunkHeader {
 	char id[4];
 	uint32_t size;
 };
 
+static_assert(sizeof(RiffChunkHeader) == 8);
+
 #endif