diff --git a/doc/Makefile b/doc/Makefile
index 470cd1f6a..04f9ba655 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -6,6 +6,7 @@
 # Default for the compiler lib search path as compiler define
 
 SGML  =	ar65.sgml	\
+        c64.sgml        \
 	ca65.sgml	\
 	cc65.sgml	\
 	cl65.sgml   	\