diff --git a/test/fuzz.c b/test/fuzz.c
index ca267a0a..1c5dec32 100644
--- a/test/fuzz.c
+++ b/test/fuzz.c
@@ -2,6 +2,7 @@
 #define MG_ENABLE_LOG 0
 #define MG_ENABLE_LINES 1
 #define MG_ENABLE_TCPIP 1
+#define MG_IO_SIZE (4 * 1024 * 1024)  // 4M IO size, unless resize is too slow
 
 #include "mongoose.c"