diff --git a/configure b/configure
index 3677035..f5b20fd 100755
--- a/configure
+++ b/configure
@@ -9288,6 +9288,11 @@ rm -rf conftest*
 
 printf "%s\n" "#define TCL_MAJOR_VERSION 8" >>confdefs.h
 
+    fi
+    if test "${TCL_MAJOR_VERSION}" -gt 8 -a x"${with_tk8}" != x; then
+
+printf "%s\n" "#define TK_MAJOR_VERSION 8" >>confdefs.h
+
     fi
     if test "${TEA_PLATFORM}" = "windows" ; then
 	if test "${SHARED_BUILD}" = "1" ; then
diff --git a/win/rules.vc b/win/rules.vc
index d459559..57bc770 100644
--- a/win/rules.vc
+++ b/win/rules.vc
@@ -24,7 +24,7 @@ _RULES_VC = 1
 # For modifications that are not backward-compatible, you *must* change
 # the major version.
 RULES_VERSION_MAJOR = 1
-RULES_VERSION_MINOR = 12
+RULES_VERSION_MINOR = 13
 
 # The PROJECT macro must be defined by parent makefile.
 !if "$(PROJECT)" == ""
@@ -881,6 +881,10 @@ USE_THREAD_ALLOC= 0
 !message *** Build for Tcl8
 TCL_BUILD_FOR = 8
 !endif
+!if [nmakehlp -f $(OPTS) "tk8"]
+!message *** Build for Tk8
+TK_BUILD_FOR = 8
+!endif
 
 !if $(TCL_MAJOR_VERSION) == 8
 !if [nmakehlp -f $(OPTS) "time64bit"]
@@ -1451,6 +1455,9 @@ OPTDEFINES	= $(OPTDEFINES) /D_USE_64BIT_TIME_T=1
 !if "$(TCL_BUILD_FOR)" == "8"
 OPTDEFINES	= $(OPTDEFINES) /DTCL_MAJOR_VERSION=8
 !endif
+!if "$(TK_BUILD_FOR)" == "8"
+OPTDEFINES	= $(OPTDEFINES) /DTK_MAJOR_VERSION=8
+!endif
 
 # Like the TEA system only set this non empty for non-Tk extensions
 # Note: some extensions use PACKAGE_NAME and others use PACKAGE_TCLNAME