diff --git a/go.mod b/go.mod
index 73860fa..9e70e27 100644
--- a/go.mod
+++ b/go.mod
@@ -13,6 +13,7 @@ require (
 	github.com/go-playground/validator/v10 v10.17.0
 	github.com/golang-jwt/jwt/v5 v5.2.0
 	github.com/gorilla/mux v1.8.1
+	github.com/huandu/xstrings v1.4.0
 	github.com/jellydator/ttlcache/v3 v3.1.1
 	github.com/mediocregopher/radix/v4 v4.1.4
 	github.com/spf13/cobra v1.8.0
diff --git a/go.sum b/go.sum
index 25cbeac..6306915 100644
--- a/go.sum
+++ b/go.sum
@@ -64,6 +64,8 @@ github.com/h2non/parth v0.0.0-20190131123155-b4df798d6542 h1:2VTzZjLZBgl62/EtslC
 github.com/h2non/parth v0.0.0-20190131123155-b4df798d6542/go.mod h1:Ow0tF8D4Kplbc8s8sSb3V2oUCygFHVp8gC3Dn6U4MNI=
 github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
 github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
+github.com/huandu/xstrings v1.4.0 h1:D17IlohoQq4UcpqD7fDk80P7l+lwAmlFaBHgOipl2FU=
+github.com/huandu/xstrings v1.4.0/go.mod h1:y5/lhBue+AyNmUVz9RLU9xbLR0o4KIIExikq4ovT0aE=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/jellydator/ttlcache/v3 v3.1.1 h1:RCgYJqo3jgvhl+fEWvjNW8thxGWsgxi+TPhRir1Y9y8=
diff --git a/internal/http/profiles.go b/internal/http/profiles.go
index 7399030..04bf2cc 100644
--- a/internal/http/profiles.go
+++ b/internal/http/profiles.go
@@ -7,6 +7,7 @@ import (
 	"net/http"
 
 	"github.com/gorilla/mux"
+	"github.com/huandu/xstrings"
 	"go.opentelemetry.io/otel/metric"
 	"go.uber.org/multierr"
 
@@ -71,7 +72,16 @@ func (p *ProfilesApi) postProfileHandler(resp http.ResponseWriter, req *http.Req
 	if err != nil {
 		var v *profiles.ValidationError
 		if errors.As(err, &v) {
+			// Manager returns ValidationError according to the struct fields names.
+			// They are uppercased, but otherwise the same as the names in the API.
+			// So to make them consistent it's enough just to make the first lowercased.
+			for field, errors := range v.Errors {
+				v.Errors[xstrings.FirstRuneToLower(field)] = errors
+				delete(v.Errors, field)
+			}
+
 			apiBadRequest(resp, v.Errors)
+
 			return
 		}
 
diff --git a/internal/http/profiles_test.go b/internal/http/profiles_test.go
index d6e4207..9033058 100644
--- a/internal/http/profiles_test.go
+++ b/internal/http/profiles_test.go
@@ -101,7 +101,7 @@ func (t *ProfilesTestSuite) TestPostProfile() {
 	t.Run("receive validation errors", func() {
 		t.ProfilesManager.On("PersistProfile", mock.Anything, mock.Anything).Once().Return(&profiles.ValidationError{
 			Errors: map[string][]string{
-				"mock": {"error1", "error2"},
+				"Username": {"error1", "error2"},
 			},
 		})
 
@@ -116,7 +116,7 @@ func (t *ProfilesTestSuite) TestPostProfile() {
 		body, _ := io.ReadAll(result.Body)
 		t.JSONEq(`{
 			"errors": {
-				"mock": [
+				"username": [
 					"error1",
 					"error2"
 				]