diff --git a/c-programming/io/freadln.c b/c-programming/io/freadln.c
index ed58735..119a875 100644
--- a/c-programming/io/freadln.c
+++ b/c-programming/io/freadln.c
@@ -89,6 +89,7 @@ int freadln(FILE* f, char** output, size_t* length_out) {
 #  define SLEEP_FN usleep
 #  define DO_SLEEP 1
 # else
+#  define SLEEP_FN(...)
 #  define DO_SLEEP 0
 # endif
 # if DO_SLEEP