diff --git a/src/scim2_filter_parser/lexer.py b/src/scim2_filter_parser/lexer.py
index 538549e..32b80bf 100644
--- a/src/scim2_filter_parser/lexer.py
+++ b/src/scim2_filter_parser/lexer.py
@@ -202,7 +202,7 @@ def SUBATTR(self, t):
     FALSE = r"false"
     TRUE = r"true"
     NULL = r"null"
-    NUMBER = r"[0-9]"  # only support integers at this time
+    NUMBER = r"[0-9]+"  # only support integers at this time
 
     # attrPath parts
     @_(r"[a-zA-Z]+:[a-zA-Z0-9:\._-]+:")