diff --git a/controllers/argocd/argocd_controller.go b/controllers/argocd/argocd_controller.go
index 7a24637..06d69ef 100644
--- a/controllers/argocd/argocd_controller.go
+++ b/controllers/argocd/argocd_controller.go
@@ -3,6 +3,7 @@ package argocd
 import (
 	"context"
 	"os"
+	"sort"
 	"strconv"
 	"strings"
 
@@ -214,6 +215,9 @@ func (r *Reconciler) Reconcile(req ctrl.Request) (ctrl.Result, error) {
 		}
 		slice = add(slice, req.Namespace)
 
+		// sort namespaces
+		sort.Strings(slice)
+
 		values["namespaces"] = slice
 	}
 
diff --git a/controllers/argocd/argocd_controller_test.go b/controllers/argocd/argocd_controller_test.go
index ca979ec..00cec50 100644
--- a/controllers/argocd/argocd_controller_test.go
+++ b/controllers/argocd/argocd_controller_test.go
@@ -609,7 +609,7 @@ var _ = Describe("Reconciler", func() {
 
 			mockHelm.
 				EXPECT().
-				Upgrade(argocd.Name, gomock.Any(), Values("namespaces", []string{"myapp3", "myapp4", "default"}), true).
+				Upgrade(argocd.Name, gomock.Any(), Values("namespaces", []string{"default", "myapp3", "myapp4"}), true).
 				Return(nil)
 
 			testReconcile(mockHelm, argocd, namespaces...)