diff --git a/pyltk/documentclass.py b/pyltk/documentclass.py
index 72e85dc..ff12231 100644
--- a/pyltk/documentclass.py
+++ b/pyltk/documentclass.py
@@ -144,9 +144,9 @@ class documentclass(element):
 
             # Content has not changed
             if old_content == new_content \
-                and os.path.exists('{}.pdf'.format(outfile)) \
+                and os.path.exists(os.path.join(outdir, outfile) + '.pdf') \
                 and os.path.getctime(infile) <= \
-                    os.path.getctime('{}.pdf'.format(outfile)):
+                    os.path.getctime(os.path.join(outdir, outfile) + '.pdf'):
                 to_create = False
 
         if to_create: