diff --git a/src/qutip_qip/circuit/texrenderer.py b/src/qutip_qip/circuit/texrenderer.py
index c668eeec..94818f0a 100644
--- a/src/qutip_qip/circuit/texrenderer.py
+++ b/src/qutip_qip/circuit/texrenderer.py
@@ -264,10 +264,12 @@ def _crop_pdf(self, filename):
             )
 
     @staticmethod
-    def _convert_pdf(file_stem):
+    def _convert_pdf(file_stem, dpi=None):
         """
         'Convert' to pdf: since LaTeX outputs a PDF file, there's nothing to do.
         """
+        if dpi is not None:
+            warnings.warn("argument dpi is ignored for pdf output.")
         with open(file_stem + ".pdf", "rb") as file:
             return file.read()