diff --git a/usr.bin/lex/lex.1 b/usr.bin/lex/lex.1
index 697c4825129..e135a49d7ec 100644
--- a/usr.bin/lex/lex.1
+++ b/usr.bin/lex/lex.1
@@ -492,7 +492,7 @@ For example, the following character classes are all equivalent:
 .nf
 
     [[:alnum:]]
-    [[:alpha:][:digit:]
+    [[:alpha:][:digit:]]
     [[:alpha:]0-9]
     [a-zA-Z0-9]