diff --git a/client/image_pull_test.go b/client/image_pull_test.go
index ebb9d9a4ad..a35e38b018 100644
--- a/client/image_pull_test.go
+++ b/client/image_pull_test.go
@@ -82,7 +82,7 @@ func TestImagePullWithPrivilegedFuncNoError(t *testing.T) {
 	client := &Client{
 		client: newMockClient(func(req *http.Request) (*http.Response, error) {
 			if !strings.HasPrefix(req.URL.Path, expectedURL) {
-				return nil, fmt.Errorf("Expected URL '%s', got '%s'", expectedURL, req.URL)
+				return nil, fmt.Errorf("expected URL '%s', got '%s'", expectedURL, req.URL)
 			}
 			auth := req.Header.Get(registry.AuthHeader)
 			if auth == "NotValid" {
@@ -92,7 +92,7 @@ func TestImagePullWithPrivilegedFuncNoError(t *testing.T) {
 				}, nil
 			}
 			if auth != "IAmValid" {
-				return nil, fmt.Errorf("Invalid auth header : expected %s, got %s", "IAmValid", auth)
+				return nil, fmt.Errorf("invalid auth header: expected %s, got %s", "IAmValid", auth)
 			}
 			query := req.URL.Query()
 			fromImage := query.Get("fromImage")
diff --git a/client/image_push_test.go b/client/image_push_test.go
index bd4b0b2fe3..ebf61572b7 100644
--- a/client/image_push_test.go
+++ b/client/image_push_test.go
@@ -97,7 +97,7 @@ func TestImagePushWithPrivilegedFuncNoError(t *testing.T) {
 				}, nil
 			}
 			if auth != "IAmValid" {
-				return nil, fmt.Errorf("Invalid auth header : expected %s, got %s", "IAmValid", auth)
+				return nil, fmt.Errorf("invalid auth header: expected %s, got %s", "IAmValid", auth)
 			}
 			query := req.URL.Query()
 			tag := query.Get("tag")
diff --git a/client/image_search_test.go b/client/image_search_test.go
index ef1923b806..56e5c7c2cb 100644
--- a/client/image_search_test.go
+++ b/client/image_search_test.go
@@ -81,7 +81,7 @@ func TestImageSearchWithPrivilegedFuncNoError(t *testing.T) {
 				}, nil
 			}
 			if auth != "IAmValid" {
-				return nil, fmt.Errorf("Invalid auth header : expected 'IAmValid', got %s", auth)
+				return nil, fmt.Errorf("invalid auth header: expected 'IAmValid', got %s", auth)
 			}
 			query := req.URL.Query()
 			term := query.Get("term")
diff --git a/client/plugin_push_test.go b/client/plugin_push_test.go
index 721bd72512..ba49211f3c 100644
--- a/client/plugin_push_test.go
+++ b/client/plugin_push_test.go
@@ -37,7 +37,7 @@ func TestPluginPush(t *testing.T) {
 			}
 			auth := req.Header.Get(registry.AuthHeader)
 			if auth != "authtoken" {
-				return nil, fmt.Errorf("invalid auth header : expected 'authtoken', got %s", auth)
+				return nil, fmt.Errorf("invalid auth header: expected 'authtoken', got %s", auth)
 			}
 			return &http.Response{
 				StatusCode: http.StatusOK,