diff --git a/src/makeg95.env b/src/makeg95.env
index 46c9254159..223c31c385 100644
--- a/src/makeg95.env
+++ b/src/makeg95.env
@@ -18,6 +18,12 @@ MINGW32=1
 MINGW32VERSION=2.95
 #MINGW32VERSION=3.0
 
+# If we're using MSYS, or other utilities that
+# use forward slashes, we need to set this when
+# invoking the makefile from DOS, or the wrong separators
+# will be assumed.
+#OSTYPE=msys
+
 # If building DLL, the version
 WXVERSION=233