diff --git a/preamble.sty b/preamble.sty
index 0e04131..4144208 100644
--- a/preamble.sty
+++ b/preamble.sty
@@ -159,6 +159,7 @@
 \newcommand{\cm}{\mathcal{M}}
 \newcommand{\cf}{\mathcal{F}}
 \newcommand{\ce}{\mathcal{E}}
+\newcommand{\ci}{\mathcal{I}}
 \newcommand{\pow}[1]{\mathcal{P}\paren{#1}}
 \newcommand{\cb}{\mathcal{B}}
 \newcommand{\cn}{\mathcal{N}}