diff --git a/src/Language/Wasm/Lexer.x b/src/Language/Wasm/Lexer.x
index 365a266..1c6a16a 100644
--- a/src/Language/Wasm/Lexer.x
+++ b/src/Language/Wasm/Lexer.x
@@ -40,8 +40,8 @@ $doublequote = \"
 @linecomment = ";;" $linechar* \x0A
 @startblockcomment = "(;"
 @endblockcomment = ";)"
-@num = $digit (\_? $digit*)*
-@hexnum = $hexdigit (\_? $hexdigit*)*
+@num = $digit (\_? $digit+)*
+@hexnum = $hexdigit (\_? $hexdigit+)*
 @id = "$" $idchar+
 @floatfrac = @num "." (@num)?
 @exp = [Ee] $sign? @num