diff --git a/git-mergetool.sh b/git-mergetool.sh
index 1355fcb19f..c1fde41a08 100755
--- a/git-mergetool.sh
+++ b/git-mergetool.sh
@@ -280,7 +280,7 @@ done
 if test -z "$merge_tool"; then
     merge_tool=`git-config merge.tool`
     case "$merge_tool" in
-	kdiff3 | tkdiff | xxdiff | meld | emerge | vimdiff)
+	kdiff3 | tkdiff | xxdiff | meld | emerge | vimdiff | "")
 	    ;; # happy
 	*)
 	    echo >&2 "git config option merge.tool set to unknown tool: $merge_tool"