diff --git a/device_types/SMU.py b/device_types/SMU.py
index 5fd8515..c31e302 100644
--- a/device_types/SMU.py
+++ b/device_types/SMU.py
@@ -91,6 +91,21 @@ def set_range(self, unit: ChannelUnit, channel_idx: ChannelIndex, mode: SMUMode,
             -> None:
         pass
 
+    @abstractmethod
+    def toggle_filter(self, channel_idx: ChannelIndex, enable: bool, check_errors: bool = False) \
+            -> None:
+        pass
+
+    @abstractmethod
+    def set_filter_type(self, channel_idx: ChannelIndex, filter_type: SMUFilterType, check_errors: bool = False) \
+            -> None:
+        pass
+
+    @abstractmethod
+    def set_filter_count(self, channel_idx: ChannelIndex, count: int, check_errors: bool = False) \
+            -> None:
+        pass
+
     @abstractmethod
     def set_sense_mode(self, channel_idx: ChannelIndex, sense_arg: SMUSense, check_errors: bool = False) \
             -> None:
diff --git a/devices/KEI2600.py b/devices/KEI2600.py
index 38cd694..29812a2 100644
--- a/devices/KEI2600.py
+++ b/devices/KEI2600.py
@@ -114,7 +114,8 @@ def toggle_measure_analog_filter(self, channel_idx: ChannelIndex, enable: bool,
 
     def toggle_filter(self, channel_idx: ChannelIndex, enable: bool, check_errors: bool = False) \
             -> None:
-        self.execute(f'{self.__to_channel(channel_idx)}.measure.filter.enable = {self.__to_channel(channel_idx)}.{'FILTER_ON' if enable else 'FILTER_OFF'}')
+        self.execute(
+            f'{self.__to_channel(channel_idx)}.measure.filter.enable = {self.__to_channel(channel_idx)}.{"FILTER_ON" if enable else "FILTER_OFF"}')
         if check_errors:
             self.check_error_buffer()
 
diff --git a/specifications/KEI2600.json b/specifications/KEI2600.json
index c90ffd8..f73bdbc 100644
--- a/specifications/KEI2600.json
+++ b/specifications/KEI2600.json
@@ -69,7 +69,7 @@
       "name": "toggle_filter",
       "type": "generated",
       "signature": "channel_idx: ChannelIndex, enable: bool",
-      "command": "f'{self.__to_channel(channel_idx)}.measure.filter.enable = {self.__to_channel(channel_idx)}.{'FILTER_ON' if enable else 'FILTER_OFF'}'"
+      "command": "f'{self.__to_channel(channel_idx)}.measure.filter.enable = {self.__to_channel(channel_idx)}.{\"FILTER_ON\" if enable else \"FILTER_OFF\"}'"
     },
     {
       "name": "set_filter_type",