diff --git a/docs/iris.sty b/docs/iris.sty
index 5b85dfb085bd9dc3ddfe628977cc2ca2fd848f1c..f9e1dcae8513d1bca9c6e24c1b0d30f84a56139e 100644
--- a/docs/iris.sty
+++ b/docs/iris.sty
@@ -83,9 +83,10 @@
 
 \newcommand{\subst}[3]{{#1}[{#3} / {#2}]}
 
-\newcommand{\mapinsert}[3]{#3[#1:=#2]}
-\newcommand{\mapsingleton}[2]{[#1:=#2]}
-\newcommand{\mapsingletonComp}[3]{\left[ #1 := #2 \spac\middle|\spac #3 \right]}
+\newcommand{\mapinsert}[3]{#3[#1\mathop{\vcentcolon=}#2]}
+\newcommand{\mapsingleton}[2]{[#1\mathop{\vcentcolon=}#2]}
+\newcommand{\mapsingletonComp}[3]
+  {\left[ #1 \mathop{\vcentcolon=} #2 \spac\middle|\spac #3 \right]}
 
 \newcommand{\nil}{\epsilon}