diff --git a/setup.py b/setup.py
index 5e515940f..decd14d5d 100644
--- a/setup.py
+++ b/setup.py
@@ -634,6 +634,7 @@ def get_mupdf():
     else:
         # Use installed MuPDF.
         log( f'Using system mupdf.')
+        unix_build_type = ''
     
     # Set include and library paths for building PyMuPDF.
     #