Add entry for weakref documentation.
diff --git a/Doc/Makefile.deps b/Doc/Makefile.deps
index 2fe792e..bfba9b7 100644
--- a/Doc/Makefile.deps
+++ b/Doc/Makefile.deps
@@ -53,6 +53,7 @@
 	../lib/libsys.tex \
 	../lib/libfpectl.tex \
 	../lib/libgc.tex \
+	../lib/libweakref.tex \
 	../lib/libtypes.tex \
 	../lib/libtraceback.tex \
 	../lib/libpickle.tex \