diff --git a/lib/post-merge b/lib/post-merge
index 7e248b5..cb7c130 100755
--- a/lib/post-merge
+++ b/lib/post-merge
@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/zsh
 # -*- zsh -*-
 
 local_hook="$HOME"/.git_template.local/hooks/post-merge
@@ -6,5 +6,4 @@ local_hook="$HOME"/.git_template.local/hooks/post-merge
 
 .git/hooks/ctags >/dev/null 2>&1 &
 
-make update
-
+(($+commands[gmake])) && gmake update || make update
diff --git a/lib/shared.mk b/lib/shared.mk
index 3081c22..8f4bcac 100644
--- a/lib/shared.mk
+++ b/lib/shared.mk
@@ -4,6 +4,13 @@ ifndef _SHELL
 endif
 SHELL := $(_SHELL)
 
+ifeq ($(shell $(MAKE) -v | grep GNU),)
+  $(error I need gnumake not bsdmake)
+endif
+REQUIRED_V := 3.82
+ifneq ($(REQUIRED_V),$(firstword $(sort $(MAKE_VERSION) $(REQUIRED_V))))
+  $(error For .ONESHELL to work I need at least version $(REQUIRED_V))
+endif
 .ONESHELL:
 
 # Helper scripts for setting up and taking down links.