diff --git a/src/Make_cyg_ming.mak b/src/Make_cyg_ming.mak
index 24c1338504d27..8654ca3a51810 100644
--- a/src/Make_cyg_ming.mak
+++ b/src/Make_cyg_ming.mak
@@ -1082,6 +1082,13 @@ endif
 	$(MAKE) -C xxd -f Make_ming.mak clean
 	$(MAKE) -C tee clean
 
+# Run vim script to generate the Ex command lookup table.
+# This only needs to be run when a command name has been added or changed.
+# If this fails because you don't have Vim yet, first build and install Vim
+# without changes.
+cmdidxs: ex_cmds.h
+	vim --clean -X -u create_cmdidxs.vim
+
 ###########################################################################
 INCL =	vim.h alloc.h ascii.h ex_cmds.h feature.h globals.h \
 	keymap.h macros.h option.h os_dos.h os_win32.h proto.h regexp.h \
@@ -1128,6 +1135,8 @@ endif
 $(OUTDIR):
 	$(MKDIR) $(OUTDIR)
 
+$(OUTDIR)/ex_docmd.o: ex_docmd.c $(INCL) ex_cmdidxs.h
+
 $(OUTDIR)/gui_dwrite.o:	gui_dwrite.cpp gui_dwrite.h
 	$(CC) -c $(CFLAGS) $(CXXFLAGS) gui_dwrite.cpp -o $@
 
diff --git a/src/Make_mvc.mak b/src/Make_mvc.mak
index 1a74d3bb3e200..65967b61d7393 100644
--- a/src/Make_mvc.mak
+++ b/src/Make_mvc.mak
@@ -1411,6 +1411,13 @@ clean: testclean
 	$(MAKE) /NOLOGO -f Makefile clean
 	cd ..
 
+# Run vim script to generate the Ex command lookup table.
+# This only needs to be run when a command name has been added or changed.
+# If this fails because you don't have Vim yet, first build and install Vim
+# without changes.
+cmdidxs: ex_cmds.h
+	vim --clean -X -u create_cmdidxs.vim
+
 test:
 	cd testdir
 	$(MAKE) /NOLOGO -f Make_dos.mak win32
@@ -1530,7 +1537,7 @@ $(OUTDIR)/ex_cmds.obj:	$(OUTDIR) ex_cmds.c  $(INCL)
 
 $(OUTDIR)/ex_cmds2.obj:	$(OUTDIR) ex_cmds2.c  $(INCL)
 
-$(OUTDIR)/ex_docmd.obj:	$(OUTDIR) ex_docmd.c  $(INCL)
+$(OUTDIR)/ex_docmd.obj:	$(OUTDIR) ex_docmd.c  $(INCL) ex_cmdidxs.h
 
 $(OUTDIR)/ex_eval.obj:	$(OUTDIR) ex_eval.c  $(INCL)
 
diff --git a/src/Make_vms.mms b/src/Make_vms.mms
index f635d56027a27..0a916310fe001 100644
--- a/src/Make_vms.mms
+++ b/src/Make_vms.mms
@@ -765,7 +765,7 @@ ex_cmds2.obj : ex_cmds2.c vim.h [.auto]config.h feature.h os_unix.h \
 ex_docmd.obj : ex_docmd.c vim.h [.auto]config.h feature.h os_unix.h \
  ascii.h keymap.h term.h macros.h structs.h regexp.h \
  gui.h beval.h [.proto]gui_beval.pro option.h ex_cmds.h proto.h \
- globals.h
+ globals.h ex_cmdidxs.h
 ex_eval.obj : ex_eval.c vim.h [.auto]config.h feature.h os_unix.h \
  ascii.h keymap.h term.h macros.h structs.h regexp.h \
  gui.h beval.h [.proto]gui_beval.pro option.h ex_cmds.h proto.h \