diff --git a/src/runtime/defs_openbsd.go b/src/runtime/defs_openbsd.go
index 8d323449d1..f818dc4453 100644
--- a/src/runtime/defs_openbsd.go
+++ b/src/runtime/defs_openbsd.go
@@ -26,6 +26,7 @@ package runtime
 #include <sys/signal.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <pthread.h>
 #include <signal.h>
 */
 import "C"