Index: uspace/lib/libc/generic/time.c
===================================================================
--- uspace/lib/libc/generic/time.c	(revision 2e51969e2c8c3905ceef1d73437f34d14c927dff)
+++ uspace/lib/libc/generic/time.c	(revision 0c09f2b5b069871c49c79e41106502db160094db)
@@ -188,5 +188,5 @@
 
 /** Wait unconditionally for specified number of microseconds */
-void usleep(unsigned long usec)
+int usleep(unsigned long usec)
 {
 	atomic_t futex = FUTEX_INITIALIZER;
@@ -194,4 +194,5 @@
 	futex_initialize(&futex, 0);
 	futex_down_timeout(&futex, usec, 0);
+	return 0;
 }
 
@@ -211,4 +212,5 @@
 		seconds -= period;
 	}
+	return 0;
 }
 
Index: uspace/lib/libc/include/unistd.h
===================================================================
--- uspace/lib/libc/include/unistd.h	(revision 2e51969e2c8c3905ceef1d73437f34d14c927dff)
+++ uspace/lib/libc/include/unistd.h	(revision 0c09f2b5b069871c49c79e41106502db160094db)
@@ -46,5 +46,5 @@
 extern void _exit(int status);
 extern void *sbrk(ssize_t incr);
-extern void usleep(unsigned long usec);
+extern int usleep(unsigned long usec);
 extern unsigned int sleep(unsigned int seconds);