diff --git a/stackit/internal/services/sqlserverflexbeta/user/datasource.go b/stackit/internal/services/sqlserverflexbeta/user/datasource.go
index 68a20378..3ffaa68b 100644
--- a/stackit/internal/services/sqlserverflexbeta/user/datasource.go
+++ b/stackit/internal/services/sqlserverflexbeta/user/datasource.go
@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"strconv"
 
 	"github.com/hashicorp/terraform-plugin-framework/datasource"
 	"github.com/hashicorp/terraform-plugin-framework/types"
@@ -104,7 +105,7 @@ func (d *userDataSource) Read(ctx context.Context, req datasource.ReadRequest, r
 			"Reading user",
 			fmt.Sprintf(
 				"User with ID %q or instance with ID %q does not exist in project %q.",
-				userId,
+				strconv.FormatInt(userId, 10),
 				instanceId,
 				projectId,
 			),