diff --git a/cmd/flux/create_source_git.go b/cmd/flux/create_source_git.go
index 8c8c4a8f..4ca684bc 100644
--- a/cmd/flux/create_source_git.go
+++ b/cmd/flux/create_source_git.go
@@ -96,7 +96,7 @@ var (
 	sourceGitRSABits        flags.RSAKeyBits         = 2048
 	sourceGitECDSACurve                              = flags.ECDSACurve{Curve: elliptic.P384()}
 	sourceGitSecretRef      string
-	sourceGitImplementation string
+	sourceGitImplementation flags.GitImplementation
 )
 
 func init() {
@@ -110,7 +110,7 @@ func init() {
 	createSourceGitCmd.Flags().Var(&sourceGitRSABits, "ssh-rsa-bits", sourceGitRSABits.Description())
 	createSourceGitCmd.Flags().Var(&sourceGitECDSACurve, "ssh-ecdsa-curve", sourceGitECDSACurve.Description())
 	createSourceGitCmd.Flags().StringVarP(&sourceGitSecretRef, "secret-ref", "", "", "the name of an existing secret containing SSH or basic credentials")
-	createSourceGitCmd.Flags().StringVar(&sourceGitImplementation, "git-implementation", "", "the git implementation to use, can be 'go-git' or 'libgit2'")
+	createSourceGitCmd.Flags().Var(&sourceGitImplementation, "git-implementation", sourceGitImplementation.Description())
 
 	createSourceCmd.AddCommand(createSourceGitCmd)
 }
@@ -141,10 +141,6 @@ func createSourceGitCmdRun(cmd *cobra.Command, args []string) error {
 		return err
 	}
 
-	if !utils.ContainsItemString([]string{sourcev1.GoGitImplementation, sourcev1.LibGit2Implementation, ""}, sourceGitImplementation) {
-		return fmt.Errorf("Invalid git implementation %q", sourceGitImplementation)
-	}
-
 	gitRepository := sourcev1.GitRepository{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      name,
@@ -156,11 +152,14 @@ func createSourceGitCmdRun(cmd *cobra.Command, args []string) error {
 			Interval: metav1.Duration{
 				Duration: interval,
 			},
-			Reference:         &sourcev1.GitRepositoryRef{},
-			GitImplementation: sourceGitImplementation,
+			Reference: &sourcev1.GitRepositoryRef{},
 		},
 	}
 
+	if sourceGitImplementation != "" {
+		gitRepository.Spec.GitImplementation = sourceGitImplementation.String()
+	}
+
 	if sourceGitSemver != "" {
 		gitRepository.Spec.Reference.SemVer = sourceGitSemver
 	} else if sourceGitTag != "" {
diff --git a/docs/cmd/flux_create_source_git.md b/docs/cmd/flux_create_source_git.md
index 57532d16..2744ad05 100644
--- a/docs/cmd/flux_create_source_git.md
+++ b/docs/cmd/flux_create_source_git.md
@@ -56,7 +56,7 @@ flux create source git [name] [flags]
 
 ```
       --branch string                          git branch (default "master")
-      --git-implementation string              the git implementation to use, can be 'go-git' or 'libgit2'
+      --git-implementation gitImplementation   the Git implementation to use, available options are: (go-git, libgit2)
   -h, --help                                   help for git
   -p, --password string                        basic authentication password
       --secret-ref string                      the name of an existing secret containing SSH or basic credentials
diff --git a/internal/flags/git_implementation.go b/internal/flags/git_implementation.go
new file mode 100644
index 00000000..b6896303
--- /dev/null
+++ b/internal/flags/git_implementation.go
@@ -0,0 +1,55 @@
+/*
+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 flags
+
+import (
+	"fmt"
+	"strings"
+
+	sourcev1 "github.com/fluxcd/source-controller/api/v1beta1"
+
+	"github.com/fluxcd/flux2/internal/utils"
+)
+
+var supportedGitImplementations = []string{sourcev1.GoGitImplementation, sourcev1.LibGit2Implementation}
+
+type GitImplementation string
+
+func (i *GitImplementation) String() string {
+	return string(*i)
+}
+
+func (i *GitImplementation) Set(str string) error {
+	if str == "" {
+		return nil
+	}
+	if !utils.ContainsItemString(supportedGitImplementations, str) {
+		return fmt.Errorf("unsupported Git implementation '%s', must be one of: %s",
+			str, strings.Join(supportedGitImplementations, ", "))
+
+	}
+	*i = GitImplementation(str)
+	return nil
+}
+
+func (i *GitImplementation) Type() string {
+	return "gitImplementation"
+}
+
+func (i *GitImplementation) Description() string {
+	return fmt.Sprintf("the Git implementation to use, available options are: (%s)", strings.Join(supportedGitImplementations, ", "))
+}
diff --git a/internal/flags/git_implementation_test.go b/internal/flags/git_implementation_test.go
new file mode 100644
index 00000000..6372d4bf
--- /dev/null
+++ b/internal/flags/git_implementation_test.go
@@ -0,0 +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 flags
+
+import (
+	"testing"
+
+	sourcev1 "github.com/fluxcd/source-controller/api/v1beta1"
+)
+
+func TestGitImplementation_Set(t *testing.T) {
+	tests := []struct {
+		name      string
+		str       string
+		expect    string
+		expectErr bool
+	}{
+		{"supported", sourcev1.GoGitImplementation, sourcev1.GoGitImplementation, false},
+		{"unsupported", "unsupported", "", true},
+		{"empty", "", "", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var i GitImplementation
+			if err := i.Set(tt.str); (err != nil) != tt.expectErr {
+				t.Errorf("Set() error = %v, expectErr %v", err, tt.expectErr)
+			}
+			if str := i.String(); str != tt.expect {
+				t.Errorf("Set() = %v, expect %v", str, tt.expect)
+			}
+		})
+	}
+}