diff --git a/ale/drivers/base.py b/ale/drivers/base.py
index a1232751f3023ca4e2de12c805b243a1ce4c322a..d424540074067502261c94508d4f52aaf12d7476 100644
--- a/ale/drivers/base.py
+++ b/ale/drivers/base.py
@@ -11,23 +11,6 @@ class Driver():
     def __init__(self, file):
         self._file = file
 
-    def __enter__(self):
-        """
-        Called when the context is created. This is used
-        to get the kernels furnished.
-        """
-        if self.metakernel:
-            spice.furnsh(self.metakernel)
-        return self
-
-    def __exit__(self, exc_type, exc_val, exc_tb):
-        """
-        Called when the context goes out of scope. Once
-        this is done, the object is out of scope and the
-        kernels can be unloaded.
-        """
-        spice.unload(self.metakernel)
-
     def __str__(self):
         return str(self.to_dict())
 
@@ -236,6 +219,23 @@ class Spice():
     def metakernel(self):
         pass
 
+    def __enter__(self):
+        """
+        Called when the context is created. This is used
+        to get the kernels furnished.
+        """
+        if self.metakernel:
+            spice.furnsh(self.metakernel)
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """
+        Called when the context goes out of scope. Once
+        this is done, the object is out of scope and the
+        kernels can be unloaded.
+        """
+        spice.unload(self.metakernel)
+
     @property
     def odtx(self):
         return spice.gdpool('INS{}_OD_T_X'.format(self.ikid),0, 10)
diff --git a/ale/drivers/keys.py b/ale/drivers/keys.py
index 17551f4799d2125e390dc6dab654159bea6a4370..0b797589cb84db7ffe024289104d90676d13adaa 100644
--- a/ale/drivers/keys.py
+++ b/ale/drivers/keys.py
@@ -37,10 +37,13 @@ base = {
     'sun_velocity',
     'target_name',
     'number_of_ephemerides',
-    'fikid',
     'number_of_ephemerides'
 }
 
+filter = {
+    'fikid'
+}
+
 transverse_distortion = {
     'odtk',
     'odtx'
diff --git a/ale/drivers/mdis_driver.py b/ale/drivers/mdis_driver.py
index f03c86f198ce157fac13097b6d2e5a258eb808f5..c44a64bca996dcbf7bdb6b91e350a2d7dc4a418a 100644
--- a/ale/drivers/mdis_driver.py
+++ b/ale/drivers/mdis_driver.py
@@ -18,7 +18,7 @@ class MdisSpice(Spice, Framer):
         'MERCURY DUAL IMAGING SYSTEM WIDE ANGLE CAMERA':'MSGR_MDIS_WAC'
     }
 
-    required_keys = keys.base | keys.framer | keys.transverse_distortion
+    required_keys = keys.base | keys.framer | keys.filter | keys.transverse_distortion
 
     @property
     def metakernel(self):