diff --git a/3rdparty/mongoose/mongoose.h b/3rdparty/mongoose/mongoose.h
index f2c47a5ce83..7d9dc2f4926 100644
--- a/3rdparty/mongoose/mongoose.h
+++ b/3rdparty/mongoose/mongoose.h
@@ -20,6 +20,7 @@
 
 #define MONGOOSE_VERSION "5.6"
 
+#include <stdarg.h>     // required for va_list
 #include <stdio.h>      // required for FILE
 #include <stddef.h>     // required for size_t
 #include <sys/types.h>  // required for time_t