diff --git a/completions/makefile.completion.sh b/completions/makefile.completion.sh
index c2a833a..fd47fea 100644
--- a/completions/makefile.completion.sh
+++ b/completions/makefile.completion.sh
@@ -1,3 +1,3 @@
 # Add completion for Makefile
 # see http://stackoverflow.com/a/38415982/1472048
-complete -W "\`grep -oE '^[a-zA-Z0-9_-]+:([^=]|$)' Makefile | sed 's/[^a-zA-Z0-9_-]*$//'\`" make
+complete -W "\$(shopt -u nullglob; shopt -s nocaseglob; command grep -oE '^[a-zA-Z0-9_-]+:([^=]|\$)' *makefile 2>/dev/null | command sed 's/[^a-zA-Z0-9_-]*\$//')" make