diff --git a/lang/core/net/macfmt_func.go b/lang/core/net/macfmt_func.go
index 46b93b26..0796e267 100644
--- a/lang/core/net/macfmt_func.go
+++ b/lang/core/net/macfmt_func.go
@@ -81,13 +81,13 @@ func MacFmt(ctx context.Context, input []types.Value) (types.Value, error) {
 	if len(mac) != len("00:00:00:00:00:00") {
 		return nil, fmt.Errorf("invalid MAC address length: %s", mac)
 	}
-	_, err := net.ParseMAC(mac)
+	hw, err := net.ParseMAC(mac)
 	if err != nil {
 		return nil, err
 	}
 
 	return &types.StrValue{
-		V: strings.Replace(mac, "-", ":", -1),
+		V: hw.String(), // makes it lowercase and everything
 	}, nil
 }
 
@@ -100,12 +100,12 @@ func OldMacFmt(ctx context.Context, input []types.Value) (types.Value, error) {
 	if len(mac) != len("00:00:00:00:00:00") {
 		return nil, fmt.Errorf("invalid MAC address length: %s", mac)
 	}
-	_, err := net.ParseMAC(mac)
+	hw, err := net.ParseMAC(mac)
 	if err != nil {
 		return nil, err
 	}
 
 	return &types.StrValue{
-		V: strings.Replace(mac, ":", "-", -1),
+		V: strings.Replace(hw.String(), ":", "-", -1),
 	}, nil
 }
diff --git a/lang/core/net/macfmt_func_test.go b/lang/core/net/macfmt_func_test.go
index ed20c5ca..c2a8eb07 100644
--- a/lang/core/net/macfmt_func_test.go
+++ b/lang/core/net/macfmt_func_test.go
@@ -43,8 +43,8 @@ func TestMacFmt(t *testing.T) {
 		out     string
 		wantErr bool
 	}{
-		{"Valid mac with hyphens", "01-23-45-67-89-AB", "01:23:45:67:89:AB", false},
-		{"Valid mac with colons", "01:23:45:67:89:AB", "01:23:45:67:89:AB", false},
+		{"Valid mac with hyphens", "01-23-45-67-89-AB", "01:23:45:67:89:ab", false},
+		{"Valid mac with colons", "01:23:45:67:89:AB", "01:23:45:67:89:ab", false},
 		{"Incorrect mac length with colons", "01:23:45:67:89:AB:01:23:45:67:89:AB", "01:23:45:67:89:AB:01:23:45:67:89:AB", true},
 		{"Invalid mac", "", "", true},
 	}
@@ -73,8 +73,9 @@ func TestOldMacFmt(t *testing.T) {
 		out     string
 		wantErr bool
 	}{
-		{"Valid mac with hyphens", "01:23:45:67:89:AB", "01-23-45-67-89-AB", false},
-		{"Valid mac with colons", "01-23-45-67-89-AB", "01-23-45-67-89-AB", false},
+		{"Valid mac with hyphens", "01:23:45:67:89:AB", "01-23-45-67-89-ab", false},
+		{"Valid lowercase mac with hyphens", "01:23:45:67:89:ab", "01-23-45-67-89-ab", false},
+		{"Valid mac with colons", "01-23-45-67-89-AB", "01-23-45-67-89-ab", false},
 		{"Incorrect mac length with hyphens", "01-23-45-67-89-AB-01-23-45-67-89-AB", "01-23-45-67-89-AB-01-23-45-67-89-AB", true},
 		{"Invalid mac", "", "", true},
 	}