diff --git a/generic/tk.h b/generic/tk.h
index 51dc7fbea..481714a6a 100644
--- a/generic/tk.h
+++ b/generic/tk.h
@@ -147,8 +147,10 @@ typedef struct Tk_StyledElement_ *Tk_StyledElement;
 
 typedef const char *Tk_Uid;
 
-#if (TCL_MAJOR_VERSION == 8) && (TCL_MINOR_VERSION == 6)
-#   define Tcl_Size int
+#if (TCL_MAJOR_VERSION < 9) && (TCL_MINOR_VERSION < 7)
+#   ifndef Tcl_Size
+#	define Tcl_Size int
+#   endif
 #   define TCL_SIZE_MAX INT_MAX
 #   define TCL_SIZE_MODIFIER ""
 #endif
diff --git a/win/rules.vc b/win/rules.vc
index a8b45e16f..e39a007a1 100644
--- a/win/rules.vc
+++ b/win/rules.vc
@@ -1533,6 +1533,10 @@ INCLUDES = $(INCLUDES) -I"$(GENERICDIR)" -I"$(WIN_DIR)" -I"$(COMPATDIR)"
 # cflags contains generic flags used for building practically all object files
 cflags = -nologo -c $(COMPILERFLAGS) $(carch) $(cwarn) -Fp$(TMP_DIR)^\ $(cdebug)
 
+!if $(TCL_MAJOR_VERSION) == 8 && $(TCL_MINOR_VERSION) < 7
+cflags = $(cflags) -DTcl_Size=int
+!endif
+
 # appcflags contains $(cflags) and flags for building the application
 # object files (e.g. tclsh, or wish) pkgcflags contains $(cflags) plus
 # flags used for building shared object files The two differ in the