diff --git a/include/sys/wait.h b/include/sys/wait.h
index a7ad7cd1..c794f5d3 100644
--- a/include/sys/wait.h
+++ b/include/sys/wait.h
@@ -6,8 +6,6 @@ extern "C" {
 
 #include <features.h>
 
-#include <signal.h>
-
 #define __NEED_pid_t
 #define __NEED_id_t
 #include <bits/alltypes.h>
@@ -19,9 +17,15 @@ typedef enum {
 } idtype_t;
 
 pid_t wait (int *);
-int waitid (idtype_t, id_t, siginfo_t *, int);
 pid_t waitpid (pid_t, int *, int );
 
+#if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
+ || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \
+ || defined(_BSD_SOURCE)
+#include <signal.h>
+int waitid (idtype_t, id_t, siginfo_t *, int);
+#endif
+
 #if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
 #include <sys/resource.h>
 pid_t wait3 (int *, int, struct rusage *);