diff --git a/dlls/ntdll/unix/unix_private.h b/dlls/ntdll/unix/unix_private.h
index 3cf9ca66736..19f742c200c 100644
--- a/dlls/ntdll/unix/unix_private.h
+++ b/dlls/ntdll/unix/unix_private.h
@@ -22,6 +22,7 @@
 #define __NTDLL_UNIX_PRIVATE_H
 
 #include <pthread.h>
+#include <signal.h>
 #include "unixlib.h"
 #include "wine/list.h"