diff --git a/geomagio/residual/Calculation.py b/geomagio/residual/Calculation.py
index 8e2e2826df48f1147c3ffaefc8024b391b560497..0155df530f508a89322d40597194bfc9a84ea1c8 100644
--- a/geomagio/residual/Calculation.py
+++ b/geomagio/residual/Calculation.py
@@ -12,12 +12,7 @@ from .MeasurementType import (
     INCLINATION_TYPES,
     MARK_TYPES,
 )
-from .Measurement import (
-    AverageMeasurement,
-    Measurement,
-    average_measurement,
-    measurement_index,
-)
+from .Measurement import AverageMeasurement, Measurement, average_measurement
 from .Reading import Reading
 
 
diff --git a/geomagio/residual/Measurement.py b/geomagio/residual/Measurement.py
index 86fcd74032c62fabd3e44215bd5d09b81e4f97b7..27d98ed5c93837b2203521c29ef1d76be3870128 100644
--- a/geomagio/residual/Measurement.py
+++ b/geomagio/residual/Measurement.py
@@ -92,9 +92,9 @@ def safe_average(l: List[Optional[float]]):
 
 def safe_max(l: List[Optional[float]]):
     values = l and [f for f in l if f] or None
-    return l and numpy.nanmax(values) or None
+    return values and numpy.nanmax(values) or None
 
 
 def safe_min(l: List[Optional[float]]):
     values = l and [f for f in l if f] or None
-    return l and numpy.nanmin(values) or None
+    return values and numpy.nanmin(values) or None