diff --git a/gptel.el b/gptel.el
index a319e5c..a5687e1 100644
--- a/gptel.el
+++ b/gptel.el
@@ -402,7 +402,9 @@ Model parameters can be let-bound around calls to this function."
             (set-marker (make-marker) position buffer))))
          (full-prompt
          (cond
-          ((null prompt) (gptel--create-prompt start-marker))
+          ((null prompt) 
+           (let ((gptel--system-message system))
+             (gptel--create-prompt start-marker)))
           ((stringp prompt)
            `((:role "system" :content ,system)
              (:role "user"   :content ,prompt)))