diff --git a/src/llama_cpp_agent/gbnf_grammar_generator/gbnf_grammar_from_pydantic_models.py b/src/llama_cpp_agent/gbnf_grammar_generator/gbnf_grammar_from_pydantic_models.py
index 5551cb2..0900a3d 100644
--- a/src/llama_cpp_agent/gbnf_grammar_generator/gbnf_grammar_from_pydantic_models.py
+++ b/src/llama_cpp_agent/gbnf_grammar_generator/gbnf_grammar_from_pydantic_models.py
@@ -802,7 +802,7 @@ def get_primitive_grammar(grammar):
         [^"\\] |
         "\\" (["\\/bfnrt] | "u" [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F] [0-9a-fA-F])
       )* "\""
-ws ::= ([ \t\n]+)
+ws ::= ([ \t\n]?)
 number ::= "-"? ([0-9]+ | [0-9]+ "." [0-9]+) ([eE] [-+]? [0-9]+)?"""
 
     any_block = ""