diff --git a/python/sglang/srt/utils/common.py b/python/sglang/srt/utils/common.py
index 03174bf1f..6259e9c48 100644
--- a/python/sglang/srt/utils/common.py
+++ b/python/sglang/srt/utils/common.py
@@ -312,11 +312,13 @@ def get_bool_env_var(name: str, default: str = "false") -> bool:
     falsy_values = ("false", "0")
 
     if (value not in truthy_values) and (value not in falsy_values):
-        if value not in _warned_bool_env_var_keys:
+        # Warn once per env var key (not per value), otherwise different keys that share the
+        # same invalid value may suppress warnings incorrectly.
+        if name not in _warned_bool_env_var_keys:
             logger.warning(
                 f"get_bool_env_var({name}) see non-understandable value={value} and treat as false"
             )
-        _warned_bool_env_var_keys.add(value)
+        _warned_bool_env_var_keys.add(name)
 
     return value in truthy_values