diff --git a/documents/letter/Makefile b/documents/letter/Makefile
index c262eaf..c9d8547 100755
--- a/documents/letter/Makefile
+++ b/documents/letter/Makefile
@@ -1,5 +1,7 @@
+SOURCE = letter
+
 make:
-	pdflatex letter.tex -output-format=pdf
+	pdflatex $(SOURCE).tex -output-format=pdf
 	make clean
 
 clean: