diff --git a/src/os_macosx.m b/src/os_macosx.m
index 4ad8d26..1d88e7d 100644
--- a/src/os_macosx.m
+++ b/src/os_macosx.m
@@ -15,6 +15,10 @@
     Error: MACOS 9 is no longer supported in Vim 7
 #endif
 
+/* Avoid a conflict for the definition of Boolean between Mac header files and
+ * X11 header files. */
+#define NO_X11_INCLUDES
+
 #include "vim.h"
 #import <Cocoa/Cocoa.h>
 
diff --git a/src/version.c b/src/version.c
index 6d19c82..46e278d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -715,6 +715,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    21,
+/**/
     20,
 /**/
     19,
diff --git a/src/vim.h b/src/vim.h
index b9ce325..6c846c1 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -192,8 +192,8 @@
 #endif
 
 #ifdef NO_X11_INCLUDES
-    /* In os_mac_conv.c NO_X11_INCLUDES is defined to avoid X11 headers.
-     * Disable all X11 related things to avoid conflicts. */
+    /* In os_mac_conv.c and os_macosx.m NO_X11_INCLUDES is defined to avoid
+     * X11 headers.  Disable all X11 related things to avoid conflicts. */
 # ifdef FEAT_X11
 #  undef FEAT_X11
 # endif