diff --git a/c-programming/io/freadln.c b/c-programming/io/freadln.c
index e14a47b..9392ac3 100644
--- a/c-programming/io/freadln.c
+++ b/c-programming/io/freadln.c
@@ -85,7 +85,7 @@ int freadln(FILE* f, char** output, size_t* length_out) {
 #  define DO_SLEEP 1
 # elif defined(_WIN32) || defined(WIN32)
 #  include <windows.h>
-#  define SLEEP_FN(x) Sleep((DWORD) x)
+#  define SLEEP_FN(x) Sleep((DWORD) (x))
 #  define DO_SLEEP 1
 # elif defined(__CYGWIN__) || defined(__unix__) || (defined(__APPLE__) && \
        defined(__MACH__)) || defined(__linux__) || defined(__FreeBSD__) || \