diff --git a/src/pygama/utils.py b/src/pygama/utils.py
index 0b28a299b..147b60775 100644
--- a/src/pygama/utils.py
+++ b/src/pygama/utils.py
@@ -43,7 +43,7 @@ class NumbaPygamaDefaults(MutableMapping):
 
     def __init__(self) -> None:
         self.parallel: bool = getenv_bool("PYGAMA_PARALLEL", default=True)
-        self.fastmath: bool = getenv_bool("PYGAMA_FAST", default=True)
+        self.fastmath: bool = getenv_bool("PYGAMA_FASTMATH", default=True)
 
     def __getitem__(self, item: str) -> Any:
         return self.__dict__[item]