diff --git a/linux-user/signal.c b/linux-user/signal.c
index 6a81b11cd..5ed1d8532 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdarg.h>
+#include <unistd.h>
 #include <signal.h>
 #include <errno.h>
 #include <sys/ucontext.h>