diff --git a/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py b/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
index 2b9f9852bcb..01c940665da 100644
--- a/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
+++ b/vllm/entrypoints/openai/tool_parsers/hermes_tool_parser.py
@@ -340,8 +340,10 @@ def extract_tool_calls_streaming(
 
             # last case -- we have an update to existing arguments.
             elif cur_arguments and prev_arguments:
-                if isinstance(delta_text, str) and len(delta_text.rstrip(
-                )) >= 1 and delta_text.rstrip()[-1] == '}':
+                if isinstance(delta_text, str) \
+                        and len(delta_text.rstrip()) >= 2 \
+                        and delta_text.rstrip()[-1] == '}' \
+                        and delta_text.rstrip()[-2] == '}':
                     delta_text = delta_text.rstrip()[:-1]
 
                 logger.debug("got diff %s", delta_text)