diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index 5c7a70a2e..66073546e 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -1,3 +1,4 @@
+#include <cassert>
 #include <map>
 #include <set>