diff --git a/version.h b/version.h
index f8d748218e..a60abdd559 100644
--- a/version.h
+++ b/version.h
@@ -11,7 +11,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 5
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 231
+#define RUBY_PATCHLEVEL 232
 
 #include "ruby/version.h"
 #include "ruby/internal/abi.h"
diff --git a/win32/Makefile.sub b/win32/Makefile.sub
index ff3a43774e..8cf0b03a7f 100644
--- a/win32/Makefile.sub
+++ b/win32/Makefile.sub
@@ -158,6 +158,9 @@ OPTFLAGS = -O2b2xg-
 OPTFLAGS = -O2sy-
 !endif
 !endif
+!if !defined(incflags)
+incflags =
+!endif
 !if !defined(PLATFORM)
 PLATFORM = mswin32
 !endif
@@ -970,6 +973,7 @@ s,@WERRORFLAG@,$(WERRORFLAG),;t t
 s,@DEFS@,$(DEFS),;t t
 s,@CPPFLAGS@,$(CPPFLAGS),;t t
 s,@CXXFLAGS@,$(CXXFLAGS),;t t
+s,@incflags@,$(incflags),;t t
 s,@FFLAGS@,$(FFLAGS),;t t
 s,@LDFLAGS@,$(LDFLAGS),;t t
 s,@LIBS@,user32.lib,;t t