diff --git a/daemon/errors.go b/daemon/errors.go
index 6f9eb54039..6ab45f30e3 100644
--- a/daemon/errors.go
+++ b/daemon/errors.go
@@ -115,7 +115,7 @@ type invalidFilter struct {
 }
 
 func (e invalidFilter) Error() string {
-	msg := "Invalid filter '" + e.filter
+	msg := "invalid filter '" + e.filter
 	if e.value != nil {
 		msg += fmt.Sprintf("=%s", e.value)
 	}
diff --git a/daemon/images/image_search_test.go b/daemon/images/image_search_test.go
index de9fcc194c..c53f8c7f1b 100644
--- a/daemon/images/image_search_test.go
+++ b/daemon/images/image_search_test.go
@@ -46,31 +46,31 @@ func TestSearchRegistryForImagesErrors(t *testing.T) {
 		},
 		{
 			filtersArgs:   `{"type":{"custom":true}}`,
-			expectedError: "Invalid filter 'type'",
+			expectedError: "invalid filter 'type'",
 		},
 		{
 			filtersArgs:   `{"is-automated":{"invalid":true}}`,
-			expectedError: "Invalid filter 'is-automated=[invalid]'",
+			expectedError: "invalid filter 'is-automated=[invalid]'",
 		},
 		{
 			filtersArgs:   `{"is-automated":{"true":true,"false":true}}`,
-			expectedError: "Invalid filter 'is-automated",
+			expectedError: "invalid filter 'is-automated",
 		},
 		{
 			filtersArgs:   `{"is-official":{"invalid":true}}`,
-			expectedError: "Invalid filter 'is-official=[invalid]'",
+			expectedError: "invalid filter 'is-official=[invalid]'",
 		},
 		{
 			filtersArgs:   `{"is-official":{"true":true,"false":true}}`,
-			expectedError: "Invalid filter 'is-official",
+			expectedError: "invalid filter 'is-official",
 		},
 		{
 			filtersArgs:   `{"stars":{"invalid":true}}`,
-			expectedError: "Invalid filter 'stars=invalid'",
+			expectedError: "invalid filter 'stars=invalid'",
 		},
 		{
 			filtersArgs:   `{"stars":{"1":true,"invalid":true}}`,
-			expectedError: "Invalid filter 'stars=invalid'",
+			expectedError: "invalid filter 'stars=invalid'",
 		},
 	}
 	for index, e := range errorCases {
diff --git a/daemon/images/locals.go b/daemon/images/locals.go
index a57ea2da60..d62c345b72 100644
--- a/daemon/images/locals.go
+++ b/daemon/images/locals.go
@@ -12,7 +12,7 @@ type invalidFilter struct {
 }
 
 func (e invalidFilter) Error() string {
-	msg := "Invalid filter '" + e.filter
+	msg := "invalid filter '" + e.filter
 	if e.value != nil {
 		msg += fmt.Sprintf("=%s", e.value)
 	}
diff --git a/daemon/list_test.go b/daemon/list_test.go
index 1db783ff52..955d137aa1 100644
--- a/daemon/list_test.go
+++ b/daemon/list_test.go
@@ -91,7 +91,7 @@ func TestListInvalidFilter(t *testing.T) {
 	_, err = d.Containers(&types.ContainerListOptions{
 		Filters: f,
 	})
-	assert.Assert(t, is.Error(err, "Invalid filter 'invalid'"))
+	assert.Assert(t, is.Error(err, "invalid filter 'invalid'"))
 }
 
 func TestNameFilter(t *testing.T) {
diff --git a/integration-cli/docker_cli_images_test.go b/integration-cli/docker_cli_images_test.go
index 193cb20ab0..dbb9f893a9 100644
--- a/integration-cli/docker_cli_images_test.go
+++ b/integration-cli/docker_cli_images_test.go
@@ -68,7 +68,7 @@ func (s *DockerSuite) TestImagesOrderedByCreationDate(c *testing.T) {
 func (s *DockerSuite) TestImagesErrorWithInvalidFilterNameTest(c *testing.T) {
 	out, _, err := dockerCmdWithError("images", "-f", "FOO=123")
 	assert.ErrorContains(c, err, "")
-	assert.Assert(c, strings.Contains(out, "Invalid filter"))
+	assert.Assert(c, strings.Contains(out, "invalid filter"))
 }
 
 func (s *DockerSuite) TestImagesFilterLabelMatch(c *testing.T) {
@@ -252,7 +252,7 @@ func (s *DockerSuite) TestImagesEnsureDanglingImageOnlyListedOnce(c *testing.T)
 func (s *DockerSuite) TestImagesWithIncorrectFilter(c *testing.T) {
 	out, _, err := dockerCmdWithError("images", "-f", "dangling=invalid")
 	assert.ErrorContains(c, err, "")
-	assert.Assert(c, strings.Contains(out, "Invalid filter"))
+	assert.Assert(c, strings.Contains(out, "invalid filter"))
 }
 
 func (s *DockerSuite) TestImagesEnsureOnlyHeadsImagesShown(c *testing.T) {
diff --git a/integration-cli/docker_cli_ps_test.go b/integration-cli/docker_cli_ps_test.go
index fe625263bc..ad0fbfb1c4 100644
--- a/integration-cli/docker_cli_ps_test.go
+++ b/integration-cli/docker_cli_ps_test.go
@@ -203,7 +203,7 @@ func (s *DockerSuite) TestPsListContainersFilterStatus(c *testing.T) {
 	assert.Equal(c, RemoveOutputForExistingElements(containerOut, existingContainers), secondID)
 
 	result := cli.Docker(cli.Args("ps", "-a", "-q", "--filter=status=rubbish"), cli.WithTimeout(time.Second*60))
-	err := "Invalid filter 'status=rubbish'"
+	err := "invalid filter 'status=rubbish'"
 	if versions.LessThan(testEnv.DaemonAPIVersion(), "1.32") {
 		err = "Unrecognised filter value for status: rubbish"
 	}
diff --git a/integration-cli/docker_cli_search_test.go b/integration-cli/docker_cli_search_test.go
index bf858235cb..a61c5e7cdc 100644
--- a/integration-cli/docker_cli_search_test.go
+++ b/integration-cli/docker_cli_search_test.go
@@ -17,19 +17,19 @@ func (s *DockerSuite) TestSearchOnCentralRegistry(c *testing.T) {
 func (s *DockerSuite) TestSearchStarsOptionWithWrongParameter(c *testing.T) {
 	out, _, err := dockerCmdWithError("search", "--filter", "stars=a", "busybox")
 	assert.ErrorContains(c, err, "", out)
-	assert.Assert(c, strings.Contains(out, "Invalid filter"), "couldn't find the invalid filter warning")
+	assert.Assert(c, strings.Contains(out, "invalid filter"), "couldn't find the invalid filter warning")
 
 	out, _, err = dockerCmdWithError("search", "-f", "stars=a", "busybox")
 	assert.ErrorContains(c, err, "", out)
-	assert.Assert(c, strings.Contains(out, "Invalid filter"), "couldn't find the invalid filter warning")
+	assert.Assert(c, strings.Contains(out, "invalid filter"), "couldn't find the invalid filter warning")
 
 	out, _, err = dockerCmdWithError("search", "-f", "is-automated=a", "busybox")
 	assert.ErrorContains(c, err, "", out)
-	assert.Assert(c, strings.Contains(out, "Invalid filter"), "couldn't find the invalid filter warning")
+	assert.Assert(c, strings.Contains(out, "invalid filter"), "couldn't find the invalid filter warning")
 
 	out, _, err = dockerCmdWithError("search", "-f", "is-official=a", "busybox")
 	assert.ErrorContains(c, err, "", out)
-	assert.Assert(c, strings.Contains(out, "Invalid filter"), "couldn't find the invalid filter warning")
+	assert.Assert(c, strings.Contains(out, "invalid filter"), "couldn't find the invalid filter warning")
 }
 
 func (s *DockerSuite) TestSearchCmdOptions(c *testing.T) {
diff --git a/integration-cli/docker_cli_volume_test.go b/integration-cli/docker_cli_volume_test.go
index b7424c82af..2dae8ff43b 100644
--- a/integration-cli/docker_cli_volume_test.go
+++ b/integration-cli/docker_cli_volume_test.go
@@ -166,13 +166,13 @@ func (s *DockerSuite) TestVolumeCLILsFilterDangling(c *testing.T) {
 func (s *DockerSuite) TestVolumeCLILsErrorWithInvalidFilterName(c *testing.T) {
 	out, _, err := dockerCmdWithError("volume", "ls", "-f", "FOO=123")
 	assert.ErrorContains(c, err, "")
-	assert.Assert(c, strings.Contains(out, "Invalid filter"))
+	assert.Assert(c, strings.Contains(out, "invalid filter"))
 }
 
 func (s *DockerSuite) TestVolumeCLILsWithIncorrectFilterValue(c *testing.T) {
 	out, _, err := dockerCmdWithError("volume", "ls", "-f", "dangling=invalid")
 	assert.ErrorContains(c, err, "")
-	assert.Assert(c, strings.Contains(out, "Invalid filter"))
+	assert.Assert(c, strings.Contains(out, "invalid filter"))
 }
 
 func (s *DockerSuite) TestVolumeCLIRm(c *testing.T) {
diff --git a/plugin/errors.go b/plugin/errors.go
index 44d99b39b2..4aca5ff71d 100644
--- a/plugin/errors.go
+++ b/plugin/errors.go
@@ -32,7 +32,7 @@ type invalidFilter struct {
 }
 
 func (e invalidFilter) Error() string {
-	msg := "Invalid filter '" + e.filter
+	msg := "invalid filter '" + e.filter
 	if len(e.value) > 0 {
 		msg += fmt.Sprintf("=%s", e.value)
 	}
diff --git a/volume/service/errors.go b/volume/service/errors.go
index ce2d678dab..c735fca6cd 100644
--- a/volume/service/errors.go
+++ b/volume/service/errors.go
@@ -101,7 +101,7 @@ type invalidFilter struct {
 }
 
 func (e invalidFilter) Error() string {
-	msg := "Invalid filter '" + e.filter
+	msg := "invalid filter '" + e.filter
 	if e.value != nil {
 		msg += fmt.Sprintf("=%s", e.value)
 	}