diff --git a/internal/proxy/proxy.go b/internal/proxy/proxy.go
index 045e79d..0ef4df3 100644
--- a/internal/proxy/proxy.go
+++ b/internal/proxy/proxy.go
@@ -323,7 +323,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 			writeProblemDetail(w, http.StatusForbidden,
 				"https://api.example.com/problems/forbidden",
 				"Forbidden",
-				fmt.Sprintf("JWT validation failed: %v", err),
+				"JWT validation failed",
 				nil)
 			logging.Errorf("auth failed", err, map[string]string{
 				"path": r.URL.Path,