diff --git a/pkg/api/server.go b/pkg/api/server.go
index 02b4a548..dd51cb32 100644
--- a/pkg/api/server.go
+++ b/pkg/api/server.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"io"
 	"log/slog"
@@ -43,8 +44,21 @@ var (
 	headersContentPlain = map[string][]string{
 		http.CanonicalHeaderKey(common.HeaderContentType): []string{common.ContentTypePlain},
 	}
+	invalidPropertyResponse []byte
 )
 
+func init() {
+	var err error
+	vr := &VerificationResponse{
+		Success: false,
+		Code:    puzzle.InvalidPropertyError,
+	}
+	invalidPropertyResponse, err = json.Marshal(vr)
+	if err != nil {
+		panic(err)
+	}
+}
+
 type Server struct {
 	APIHeaders      map[string][]string
 	Stage           string
@@ -282,7 +296,7 @@ func (s *Server) recaptchaVerifyHandler(w http.ResponseWriter, r *http.Request)
 		propertyID := payload.Puzzle().PropertyID()
 		if propertyExternalID := db.UUIDFromSiteKey(sitekey); !bytes.Equal(propertyExternalID.Bytes[:], propertyID[:]) {
 			slog.WarnContext(ctx, "Expected property ID does not match", "expected", sitekey, "actual", hex.EncodeToString(propertyID[:]))
-			http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+			common.SendReponse(ctx, w, invalidPropertyResponse, common.JSONContentHeaders, common.NoCacheHeaders, s.APIHeaders)
 			return
 		}
 	}
@@ -353,7 +367,7 @@ func (s *Server) pcVerifyHandler(w http.ResponseWriter, r *http.Request) {
 		propertyID := payload.Puzzle().PropertyID()
 		if propertyExternalID := db.UUIDFromSiteKey(sitekey); !bytes.Equal(propertyExternalID.Bytes[:], propertyID[:]) {
 			slog.WarnContext(ctx, "Expected property ID does not match", "expected", sitekey, "actual", hex.EncodeToString(propertyID[:]))
-			http.Error(w, "Expected sitekey does not match solution puzzle", http.StatusBadRequest)
+			common.SendReponse(ctx, w, invalidPropertyResponse, common.JSONContentHeaders, common.NoCacheHeaders, s.APIHeaders)
 			return
 		}
 	}
diff --git a/pkg/api/verify_test.go b/pkg/api/verify_test.go
index 7597885e..060ece85 100644
--- a/pkg/api/verify_test.go
+++ b/pkg/api/verify_test.go
@@ -186,8 +186,8 @@ func TestVerifyPuzzleWrongExpectedSitekey(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if resp.StatusCode != http.StatusBadRequest {
-		t.Errorf("Unexpected submit status code %d", resp.StatusCode)
+	if err := checkSiteVerifyError(resp, puzzle.InvalidPropertyError); err != nil {
+		t.Fatal(err)
 	}
 }
 
@@ -226,8 +226,8 @@ func TestSiteVerifyWrongExpectedSitekey(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if resp.StatusCode != http.StatusBadRequest {
-		t.Errorf("Unexpected submit status code %d", resp.StatusCode)
+	if err := checkSiteVerifyError(resp, puzzle.InvalidPropertyError); err != nil {
+		t.Fatal(err)
 	}
 }
 
diff --git a/pkg/common/middlewares.go b/pkg/common/middlewares.go
index 8d43a51d..936ca71a 100644
--- a/pkg/common/middlewares.go
+++ b/pkg/common/middlewares.go
@@ -42,6 +42,9 @@ var (
 	HtmlContentHeaders = map[string][]string{
 		http.CanonicalHeaderKey(HeaderContentType): []string{ContentTypeHTML},
 	}
+	JSONContentHeaders = map[string][]string{
+		http.CanonicalHeaderKey(HeaderContentType): []string{ContentTypeJSON},
+	}
 )
 
 func NoopMiddleware(next http.Handler) http.Handler {
diff --git a/pkg/common/utils.go b/pkg/common/utils.go
index f3b9d9b5..96fc4722 100644
--- a/pkg/common/utils.go
+++ b/pkg/common/utils.go
@@ -68,6 +68,22 @@ func MaskEmail(email string, mask rune) string {
 	return prefix + xxx + suffix + "@" + parts[1]
 }
 
+func SendReponse(ctx context.Context, w http.ResponseWriter, response []byte, headers ...map[string][]string) {
+	wHeader := w.Header()
+	for _, hh := range headers {
+		for key, value := range hh {
+			wHeader[key] = value
+		}
+	}
+
+	n, err := w.Write(response)
+	if err != nil {
+		slog.ErrorContext(ctx, "Failed to send response", ErrAttr(err))
+	} else {
+		slog.Log(ctx, LevelTrace, "Sent response", "size", len(response), "sent", n)
+	}
+}
+
 func SendJSONResponse(ctx context.Context, w http.ResponseWriter, data interface{}, headers ...map[string][]string) {
 	response, err := json.Marshal(data)
 	if err != nil {