Markup fix
diff --git a/Doc/lib/libgc.tex b/Doc/lib/libgc.tex
index 54ca26c..0d3408b 100644
--- a/Doc/lib/libgc.tex
+++ b/Doc/lib/libgc.tex
@@ -35,7 +35,8 @@
\begin{funcdesc}{collect}{\optional{generation}}
With no arguments, run a full collection. The optional argument
\var{generation} may be an integer specifying which generation to collect
-(from 0 to 2). A ValueError is raised if the generation number is invalid.
+(from 0 to 2). A \exception{ValueError} is raised if the generation number
+is invalid.
The number of unreachable objects found is returned.
\versionchanged[The optional \var{generation} argument was added]{2.5}