diff --git a/src/measure/measurable-maps/simple.tex b/src/measure/measurable-maps/simple.tex
index 3c5744c..fd81329 100644
--- a/src/measure/measurable-maps/simple.tex
+++ b/src/measure/measurable-maps/simple.tex
@@ -26,7 +26,7 @@
 \label{definition:simple-function-standard-form}
     Let $(X, \cm)$ be a measurable space, $V$ be a vector space over $K \in \RC$, and $f: X \to Y$ be a simple function, then
     \[
-    f = \sum_{y \in f(X)}y \cdot \one_{\bracs{f \in Y}}
+    f = \sum_{y \in f(X)}y \cdot \one_{\bracs{f = y}}
     \]
     is the \textbf{standard form} of $f$.