diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index f9a51ba504..b84ac582f9 100644
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -172,8 +172,13 @@ run_merge_tool () {
 	vimdiff|gvimdiff)
 		if merge_mode; then
 			touch "$BACKUP"
-			"$merge_tool_path" -f -d -c "wincmd l" \
-				"$LOCAL" "$MERGED" "$REMOTE"
+			if $base_present; then
+				"$merge_tool_path" -f -d -c "wincmd J" \
+					"$MERGED" "$LOCAL" "$BASE" "$REMOTE"
+			else
+				"$merge_tool_path" -f -d -c "wincmd l" \
+					"$LOCAL" "$MERGED" "$REMOTE"
+			fi
 			check_unchanged
 		else
 			"$merge_tool_path" -f -d -c "wincmd l" \