diff --git a/src/qcodes/instrument_drivers/Keithley/Keithley_2450.py b/src/qcodes/instrument_drivers/Keithley/Keithley_2450.py
index 36b39c1f804..eaadc143053 100644
--- a/src/qcodes/instrument_drivers/Keithley/Keithley_2450.py
+++ b/src/qcodes/instrument_drivers/Keithley/Keithley_2450.py
@@ -698,6 +698,7 @@ def _set_sense_function(self, value: str) -> None:
         self.write(
             f":SENS:FUNC {value}",
         )
+        assert self.sense_function.inverse_val_mapping is not None
         sense_function = self.sense_function.inverse_val_mapping[value]
         sense = self.submodules[f"_sense_{sense_function}"]
         if not isinstance(sense, Keithley2450Sense):
@@ -728,8 +729,9 @@ def _set_source_function(self, value: str) -> None:
             )
 
         self.write(f":SOUR:FUNC {value}")
+        assert self.source_function.inverse_val_mapping is not None
         source_function = self.source_function.inverse_val_mapping[value]
-        source = self.submodules[f"_source_{source_function}"]
+        source = cast(Keithley2450Source, self.submodules[f"_source_{source_function}"])
         self.sense.sweep.setpoints = (source.sweep_axis,)
         if not isinstance(source, Keithley2450Source):
             raise RuntimeError(
diff --git a/src/qcodes/instrument_drivers/Keithley/Keithley_7510.py b/src/qcodes/instrument_drivers/Keithley/Keithley_7510.py
index f31021a03e8..17aef17051e 100644
--- a/src/qcodes/instrument_drivers/Keithley/Keithley_7510.py
+++ b/src/qcodes/instrument_drivers/Keithley/Keithley_7510.py
@@ -3,6 +3,7 @@
 import numpy as np
 
 from qcodes.instrument import (
+    InstrumentBaseKWArgs,
     InstrumentChannel,
     VisaInstrument,
     VisaInstrumentKWArgs,
@@ -455,7 +456,7 @@ def __init__(
         parent: VisaInstrument,
         name: str,
         proper_function: str,
-        **kwargs: "Unpack[VisaInstrumentKWArgs]",
+        **kwargs: "Unpack[InstrumentBaseKWArgs]",
     ) -> None:
         """
         The sense module of the Keithley 7510 DMM, based on the sense module of