diff --git a/src/strcmp.c b/src/strcmp.c
index bd42054..f2b86bb 100644
--- a/src/strcmp.c
+++ b/src/strcmp.c
@@ -18,7 +18,7 @@
 
 #include <stdio.h> /* fprintf(3), stderr */
 #include <stdlib.h> /* EXIT_FAILURE */
-#include <sysexits.h>
+#include <sysexits.h> /* EX_USAGE */
 
 static char *program_name = "strcmp";