diff --git a/controllers/artifact.go b/controllers/artifact.go
index 2eff5774..8d034f07 100644
--- a/controllers/artifact.go
+++ b/controllers/artifact.go
@@ -1,9 +1,47 @@
+/*
+Copyright 2021 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package controllers
 
 import sourcev1 "github.com/fluxcd/source-controller/api/v1beta2"
 
+type artifactSet []*sourcev1.Artifact
+
+// Diff returns true if any of the revisions in the artifactSet does not match any of the given artifacts.
+func (s artifactSet) Diff(set artifactSet) bool {
+	if len(s) != len(set) {
+		return true
+	}
+
+outer:
+	for _, j := range s {
+		for _, k := range set {
+			if k.HasRevision(j.Revision) {
+				continue outer
+			}
+		}
+		return true
+	}
+	return false
+}
+
 // hasArtifactUpdated returns true if any of the revisions in the current artifacts
 // does not match any of the artifacts in the updated artifacts
+// NOTE: artifactSet is a replacement for this. Remove this once it's not used
+// anywhere.
 func hasArtifactUpdated(current []*sourcev1.Artifact, updated []*sourcev1.Artifact) bool {
 	if len(current) != len(updated) {
 		return true
diff --git a/controllers/artifact_test.go b/controllers/artifact_test.go
index 9746dfd8..935c93bf 100644
--- a/controllers/artifact_test.go
+++ b/controllers/artifact_test.go
@@ -1,26 +1,40 @@
+/*
+Copyright 2021 The Flux authors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
 package controllers
 
 import (
 	"testing"
-
-	sourcev1 "github.com/fluxcd/source-controller/api/v1beta2"
 )
 
-func TestHasUpdated(t *testing.T) {
+func Test_artifactSet_Diff(t *testing.T) {
 	tests := []struct {
 		name     string
-		current  []*sourcev1.Artifact
-		updated  []*sourcev1.Artifact
+		current  artifactSet
+		updated  artifactSet
 		expected bool
 	}{
 		{
-			name: "not updated single",
-			current: []*sourcev1.Artifact{
+			name: "one artifact, no diff",
+			current: artifactSet{
 				{
 					Revision: "foo",
 				},
 			},
-			updated: []*sourcev1.Artifact{
+			updated: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -28,13 +42,13 @@ func TestHasUpdated(t *testing.T) {
 			expected: false,
 		},
 		{
-			name: "updated single",
-			current: []*sourcev1.Artifact{
+			name: "one artifact, diff",
+			current: artifactSet{
 				{
 					Revision: "foo",
 				},
 			},
-			updated: []*sourcev1.Artifact{
+			updated: artifactSet{
 				{
 					Revision: "bar",
 				},
@@ -42,8 +56,8 @@ func TestHasUpdated(t *testing.T) {
 			expected: true,
 		},
 		{
-			name: "not updated multiple",
-			current: []*sourcev1.Artifact{
+			name: "multiple artifacts, no diff",
+			current: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -51,7 +65,7 @@ func TestHasUpdated(t *testing.T) {
 					Revision: "bar",
 				},
 			},
-			updated: []*sourcev1.Artifact{
+			updated: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -62,8 +76,8 @@ func TestHasUpdated(t *testing.T) {
 			expected: false,
 		},
 		{
-			name: "updated multiple",
-			current: []*sourcev1.Artifact{
+			name: "multiple artifacts, diff",
+			current: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -71,7 +85,7 @@ func TestHasUpdated(t *testing.T) {
 					Revision: "bar",
 				},
 			},
-			updated: []*sourcev1.Artifact{
+			updated: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -82,8 +96,8 @@ func TestHasUpdated(t *testing.T) {
 			expected: true,
 		},
 		{
-			name: "updated different artifact count",
-			current: []*sourcev1.Artifact{
+			name: "different artifact count",
+			current: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -91,7 +105,7 @@ func TestHasUpdated(t *testing.T) {
 					Revision: "bar",
 				},
 			},
-			updated: []*sourcev1.Artifact{
+			updated: artifactSet{
 				{
 					Revision: "foo",
 				},
@@ -101,7 +115,7 @@ func TestHasUpdated(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			result := hasArtifactUpdated(tt.current, tt.updated)
+			result := tt.current.Diff(tt.updated)
 			if result != tt.expected {
 				t.Errorf("Archive() result = %v, wantResult %v", result, tt.expected)
 			}