diff --git a/lib/cpp/src/windows/config.h b/lib/cpp/src/windows/config.h
index 272a070..3af158a 100644
--- a/lib/cpp/src/windows/config.h
+++ b/lib/cpp/src/windows/config.h
@@ -72,6 +72,11 @@
 
 // Missing functions.
 #define usleep(ms) Sleep(ms)
+inline int sleep(DWORD ms)
+{
+    Sleep(ms);
+    return 0;
+}
 
 #if WINVER <= 0x0502
 #define poll(fds, nfds, timeout) \