diff --git a/groupoids.tex b/groupoids.tex
index e897d2b32..cbb6e672d 100644
--- a/groupoids.tex
+++ b/groupoids.tex
@@ -309,7 +309,7 @@ \section{Group schemes}
 $$
 \xymatrix{
 G \times_S G \ar[r]_-{f \times f} \ar[d]_m &
-G' \times_S G' \ar[d]^m \\
+G' \times_S G' \ar[d]^{m'} \\
 G \ar[r]^f & G'
 }
 $$