diff --git a/source/basic.tex b/source/basic.tex
index a813f68d9c..1fb257f49d 100644
--- a/source/basic.tex
+++ b/source/basic.tex
@@ -6806,7 +6806,7 @@
 \item $A$ happens before $B$ and
 \item there is no other
 \indextext{side effects}%
-side effect $X$ to $M$ such that $A$
+side effect $X$ on $M$ such that $A$
 happens before $X$ and $X$ happens before $B$.
 \end{itemize}