diff --git a/python-cartopy.spec b/python-cartopy.spec
index 56119f8..f7cc92d 100644
--- a/python-cartopy.spec
+++ b/python-cartopy.spec
@@ -100,9 +100,12 @@ cp -a %SOURCE1 lib/cartopy/
 # Remove bundled egg-info
 rm -rf %{srcname}.egg-info
 
+# Remove pre-generated files
+rm $(grep -rl '/\* Generated by Cython')
+
 
 %build
-%py3_build
+FORCE_CYTHON=1 %py3_build
 
 
 %install