diff --git a/httplib.h b/httplib.h
index e7366ae..3eb48b9 100644
--- a/httplib.h
+++ b/httplib.h
@@ -61,6 +61,7 @@ typedef int socket_t;
 #include <string>
 #include <thread>
 #include <sys/stat.h>
+#include <sys/select.h>
 #include <fcntl.h>
 #include <assert.h>