diff --git a/passes/cmds/exec.cc b/passes/cmds/exec.cc
index 399cb0ebb..e4676fd33 100644
--- a/passes/cmds/exec.cc
+++ b/passes/cmds/exec.cc
@@ -27,6 +27,7 @@
 #  define WIFSTOPPED(x) 0
 #  define WEXITSTATUS(x) ((x) & 0xff)
 #  define WTERMSIG(x) SIGTERM
+#  define WSTOPSIG(x) 0
 #else
 #  include <sys/wait.h>
 #endif