diff --git a/source/lex.tex b/source/lex.tex
index 6cf011e432..c05dcc3e00 100644
--- a/source/lex.tex
+++ b/source/lex.tex
@@ -499,9 +499,9 @@
 \begin{bnf}
 \nontermdef{preprocessing-token}\br
     header-name\br
-    import-keyword\br
-    module-keyword\br
-    export-keyword\br
+    \grammarterm{import-keyword}\br
+    \grammarterm{module-keyword}\br
+    \grammarterm{export-keyword}\br
     identifier\br
     pp-number\br
     character-literal\br