diff --git a/internal/handlers/filters.go b/internal/handlers/filters.go
index afe0516..b550727 100644
--- a/internal/handlers/filters.go
+++ b/internal/handlers/filters.go
@@ -103,7 +103,7 @@ func (h *FiltersHandler) GetSavedFilterByID(c *echo.Context) error {
 	// Use service layer (includes business logic + ownership verification)
 	filter, err := h.filtersService.GetSavedFilterByID(c.Request().Context(), userUUID, filterID)
 	if err != nil {
-		if err.Error() == "filter not found or access denied" {
+		if errors.Is(err, services.ErrFilterNotFound) {
 			return c.JSON(http.StatusNotFound, map[string]string{
 				"error": "filter not found",
 			})
diff --git a/internal/services/filters.go b/internal/services/filters.go
index 2ac8bbe..9a35465 100644
--- a/internal/services/filters.go
+++ b/internal/services/filters.go
@@ -4,12 +4,16 @@ import (
 	"bookhoard/internal/database"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgtype"
 )
 
+// Custom errors for saved filters
+var ErrFilterNotFound = errors.New("filter not found or access denied")
+
 type FiltersService struct {
 	db *database.Queries
 }
@@ -38,7 +42,7 @@ func (s *FiltersService) GetSavedFilterByID(ctx context.Context, userID uuid.UUI
 		UserID: pgtype.UUID{Bytes: userID, Valid: true},
 	})
 	if err != nil {
-		return database.SavedFilters{}, fmt.Errorf("filter not found or access denied: %w", err)
+		return database.SavedFilters{}, ErrFilterNotFound
 	}
 
 	return filter, nil