diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index 67cb5fe..954f34e 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -145,7 +145,7 @@
 extern int pause(void);
 extern unsigned int alarm(unsigned int);
 extern unsigned int sleep(unsigned int);
-extern void usleep(unsigned long);
+extern int usleep(unsigned long);
 
 extern int gethostname(char *, size_t);
 extern int sethostname(const char *, size_t);