diff --git a/src/core/wee-signal.c b/src/core/wee-signal.c
index d29cf6468..7a0886f53 100644
--- a/src/core/wee-signal.c
+++ b/src/core/wee-signal.c
@@ -24,6 +24,7 @@
 #endif
 
 #include <stdlib.h>
+#include <unistd.h>
 #include <string.h>
 #include <signal.h>