diff --git a/pkg/storage/compliance/tests.go b/pkg/storage/compliance/tests.go
index afee4db2..48c6fb45 100644
--- a/pkg/storage/compliance/tests.go
+++ b/pkg/storage/compliance/tests.go
@@ -25,6 +25,7 @@ func RunTests(t *testing.T, b storage.Backend, clearBackend func() error) {
 	testDelete(t, b)
 	testGet(t, b)
 	testExists(t, b)
+	testShouldNotExist(t, b)
 	testCatalog(t, b)
 }
 
@@ -166,6 +167,24 @@ func testExists(t *testing.T, b storage.Backend) {
 	require.Equal(t, true, exists)
 }
 
+func testShouldNotExist(t *testing.T, b storage.Backend) {
+	ctx := context.Background()
+	mod := "shouldNotExist"
+	ver := "v1.2.3-pre.1"
+	mock := getMockModule()
+	zipBts, _ := ioutil.ReadAll(mock.Zip)
+	err := b.Save(ctx, mod, ver, mock.Mod, bytes.NewReader(zipBts), mock.Info)
+	require.NoError(t, err, "should successfully safe a mock module")
+	defer b.Delete(ctx, mod, ver)
+
+	prefixVer := "v1.2.3-pre"
+	exists, err := b.Exists(ctx, mod, prefixVer)
+	require.NoError(t, err)
+	if exists {
+		t.Fatal("a non existing version that has the same prefix of an existing version should not exist")
+	}
+}
+
 // testDelete tests that a module can be deleted from a
 // storage Backend and the the Exists method returns false
 // afterwards.
diff --git a/pkg/storage/s3/checker.go b/pkg/storage/s3/checker.go
index 623187cf..684cc23f 100644
--- a/pkg/storage/s3/checker.go
+++ b/pkg/storage/s3/checker.go
@@ -30,6 +30,17 @@ func (s *Storage) Exists(ctx context.Context, module, version string) (bool, err
 	if err != nil {
 		return false, errors.E(op, err, errors.M(module), errors.V(version))
 	}
-
-	return len(loo.Contents) == 3, nil
+	var count int
+	for _, o := range loo.Contents {
+		// sane assumption: no duplicate keys.
+		switch *o.Key {
+		case config.PackageVersionedName(module, version, "info"):
+			count++
+		case config.PackageVersionedName(module, version, "mod"):
+			count++
+		case config.PackageVersionedName(module, version, "zip"):
+			count++
+		}
+	}
+	return count == 3, nil
 }