diff --git a/src/bin/pgbench/exprscan.l b/src/bin/pgbench/exprscan.l
index cb51a98fd6..fc7615f558 100644
--- a/src/bin/pgbench/exprscan.l
+++ b/src/bin/pgbench/exprscan.l
@@ -61,7 +61,7 @@ space			[ \t\r\f]
 					yylval.ival = strtoint64(yytext);
 					return INTEGER;
 				}
-{alpha}{alnum}+	{
+{alpha}{alnum}*	{
 					yycol += yyleng;
 					yylval.str = pg_strdup(yytext);
 					return FUNCTION;