diff --git a/glossary.tex b/glossary.tex
index a56d1ce0e9a90ac5bdc7be5fa7a9b6460f2ad766..ce66279da5d4c15a73772f78b94baa248723942f 100644
--- a/glossary.tex
+++ b/glossary.tex
@@ -269,7 +269,8 @@
 \newacronym[
   description={provide linear, measure of a character's health and injury},
   shortplural={HP},
-  prefix={a\space},
+  prefix={an\space},
+  prefixfirst={a\space},
   name={Health Points (HP)},
   ]{hp}{HP}{Health Point}