diff --git a/adafruit_bme680.py b/adafruit_bme680.py
index 5fab1d7..c4771dc 100644
--- a/adafruit_bme680.py
+++ b/adafruit_bme680.py
@@ -188,7 +188,7 @@ def filter_size(self):
     @filter_size.setter
     def filter_size(self, size):
         if size in _BME680_FILTERSIZES:
-            self._filter = _BME680_FILTERSIZES[size]
+            self._filter = _BME680_FILTERSIZES.index(size)
         else:
             raise RuntimeError("Invalid size")