diff --git a/Makefile.am b/Makefile.am
index be5abc1..0501997 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -5,6 +5,7 @@ pkgconfig_DATA = xkbcommon.pc
 
 EXTRA_DIST = \
 	makekeys.py \
+	makeheader.py \
 	src/xkbcomp/keywords.gperf \
 	test/data \
 	README.md \
@@ -317,26 +318,10 @@ bench_compose_LDADD = $(BENCH_LDADD)
 # Custom targets
 ##
 
-# This sed script strips out lines that start with '#define _' which
-# removes #define _OSF_Keysyms and such.  The XK_Ydiaeresis case is to
-# handle a duplicate definition in HPkeysyms.h which kicks in if it's
-# not already defined.
-X11_INCLUDEDIR = /usr/include/X11
-KEYSYMDEFS = \
-	 $(X11_INCLUDEDIR)/keysymdef.h \
-	 $(X11_INCLUDEDIR)/XF86keysym.h \
-	 $(X11_INCLUDEDIR)/Sunkeysym.h \
-	 $(X11_INCLUDEDIR)/DECkeysym.h \
-	 $(X11_INCLUDEDIR)/HPkeysym.h
+# Run this to regenerate xkbcommon-keysyms.h from the X11 headers
+# defining the keysyms and update the name <-> keysym mapping.
 update-keysyms:
-	echo -en '#ifndef _XKBCOMMON_KEYSYMS_H\n#define _XKBCOMMON_KEYSYMS_H\n\n' > $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
-	echo -en '/* This file is autogenerated from Makefile.am; please do not commit directly. */\n\n' >> $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
-	echo -en '#define XKB_KEY_NoSymbol                    0x000000  /* Special KeySym */\n\n' >> $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
-	sed -e '/XK_Ydiaeresis\s*0x100000ee/d' \
-	    -e '/#define _/d' \
-	    -e 's/#define\s*\(\w*\)XK_/#define XKB_KEY_\1/' \
-	    -e '/\(#ifdef\|#ifndef\|#endif\)/d' $(KEYSYMDEFS) >> $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
-	echo -en '\n\n#endif\n' >> $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
+	LC_CTYPE=C python $(top_srcdir)/makeheader.py > $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h
 	LC_CTYPE=C python $(top_srcdir)/makekeys.py $(top_srcdir)/xkbcommon/xkbcommon-keysyms.h > $(top_srcdir)/src/ks_tables.h
 
 # Run this if you add/remove a new keyword to the xkbcomp scanner,
diff --git a/makeheader.py b/makeheader.py
new file mode 100644
index 0000000..7b7a07e
--- /dev/null
+++ b/makeheader.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+
+from __future__ import print_function
+import re
+
+
+HEADERS = [
+    '/usr/include/X11/keysymdef.h',
+    '/usr/include/X11/XF86keysym.h',
+    '/usr/include/X11/Sunkeysym.h',
+    '/usr/include/X11/DECkeysym.h',
+    '/usr/include/X11/HPkeysym.h',
+]
+
+print('''#ifndef _XKBCOMMON_KEYSYMS_H
+#define _XKBCOMMON_KEYSYMS_H
+
+/* This file is autogenerated; please do not commit directly. */
+
+#define XKB_KEY_NoSymbol                    0x000000  /* Special KeySym */
+''')
+for path in HEADERS:
+    with open(path) as header:
+        for line in header:
+            if '#ifdef' in line or '#ifndef' in line or '#endif' in line:
+                continue
+
+            # Remove #define _OSF_Keysyms and such.
+            if '#define _' in line:
+                continue
+
+            # Handle a duplicate definition in HPkeysyms.h which kicks in if
+            # it's not already defined.
+            if 'XK_Ydiaeresis' in line and '0x100000ee' in line:
+                continue
+
+            line = re.sub(r'#define\s*(\w*)XK_', r'#define XKB_KEY_\1', line)
+
+            print(line, end='')
+print('\n\n#endif')
diff --git a/xkbcommon/xkbcommon-keysyms.h b/xkbcommon/xkbcommon-keysyms.h
index ef862dd..bd172a6 100644
--- a/xkbcommon/xkbcommon-keysyms.h
+++ b/xkbcommon/xkbcommon-keysyms.h
@@ -1,7 +1,7 @@
 #ifndef _XKBCOMMON_KEYSYMS_H
 #define _XKBCOMMON_KEYSYMS_H
 
-/* This file is autogenerated from Makefile.am; please do not commit directly. */
+/* This file is autogenerated; please do not commit directly. */
 
 #define XKB_KEY_NoSymbol                    0x000000  /* Special KeySym */