diff --git a/mergetools/vimdiff b/mergetools/vimdiff
index 734d15a03b..f8ad6b35d4 100644
--- a/mergetools/vimdiff
+++ b/mergetools/vimdiff
@@ -325,7 +325,7 @@ gen_cmd () {
 		fi
 
 		# If this is a single window diff with all the buffers
-		if ! echo "$tab" | grep ",\|/" >/dev/null
+		if ! echo "$tab" | grep -E ",|/" >/dev/null
 		then
 			CMD="$CMD | silent execute 'bufdo diffthis'"
 		fi
diff --git a/t/t1404-update-ref-errors.sh b/t/t1404-update-ref-errors.sh
index 98e9158bd2..67ebd81a4c 100755
--- a/t/t1404-update-ref-errors.sh
+++ b/t/t1404-update-ref-errors.sh
@@ -100,7 +100,7 @@ df_test() {
 		printf "%s\n" "delete $delname" "create $addname $D"
 	fi >commands &&
 	test_must_fail git update-ref --stdin <commands 2>output.err &&
-	grep "fatal:\( cannot lock ref $SQ$addname$SQ:\)\? $SQ$delref$SQ exists; cannot create $SQ$addref$SQ" output.err &&
+	grep -E "fatal:( cannot lock ref $SQ$addname$SQ:)? $SQ$delref$SQ exists; cannot create $SQ$addref$SQ" output.err &&
 	printf "%s\n" "$C $delref" >expected-refs &&
 	git for-each-ref --format="%(objectname) %(refname)" $prefix/r >actual-refs &&
 	test_cmp expected-refs actual-refs