diff --git a/libs/ardour/diskstream.cc b/libs/ardour/diskstream.cc
index 9312de5bf1..a9a5c6ce07 100644
--- a/libs/ardour/diskstream.cc
+++ b/libs/ardour/diskstream.cc
@@ -19,6 +19,7 @@
 */
 
 #include <fstream>
+#include <cassert>
 #include <cstdio>
 #include <unistd.h>
 #include <cmath>