diff --git a/makefiles/Makefile.third_party.unix b/makefiles/Makefile.third_party.unix
index ee2978f7cc..10e02fbb73 100644
--- a/makefiles/Makefile.third_party.unix
+++ b/makefiles/Makefile.third_party.unix
@@ -11,7 +11,7 @@ SWIG_TAG = 3.0.5
 # version 8.33
 PCRE_TAG = 1336
 # Mono version.
-MONO_TAG = 3.10.0
+MONO_TAG = 4.0.1
 # BISON, FLEX
 BISON_TAG = 3.0.4
 FLEX_TAG = 2.5.37