diff --git a/lib/obstacle.h b/lib/obstacle.h
index 7d7bcac7..3cd98cbb 100644
--- a/lib/obstacle.h
+++ b/lib/obstacle.h
@@ -12,6 +12,7 @@
 
 #include "lib/event.h"
 #include "lib/locking.h"
+#include "lib/string.h"
 #include "lib/tlists.h"
 
 #define TLIST_PREFIX obstacle