diff --git a/massql/msql.ebnf b/massql/msql.ebnf
index 47fdc28..e6591b4 100644
--- a/massql/msql.ebnf
+++ b/massql/msql.ebnf
@@ -153,7 +153,7 @@ divide: "/"
 plus: "+"
 minus: "-"
 
-moleculeformula: /[A-Z][A-Za-z1-9]*/
+moleculeformula: /[A-Z][A-Za-z0-9]*/
 aminoacids: /[A-Z][A-Z]*/
 peptide: /[A-Z][A-Z]*/
 peptidecharge: /[1-9]/
@@ -163,4 +163,4 @@ peptideion: /[A-Za-z]/
 %import common.ESCAPED_STRING   -> STRING
 %import common.SIGNED_NUMBER    -> NUMBER
 %import common.WS
-%ignore WS
\ No newline at end of file
+%ignore WS