diff --git a/src/common/actionflow.py b/src/common/actionflow.py
index 398dcd2..9ff4ab2 100644
--- a/src/common/actionflow.py
+++ b/src/common/actionflow.py
@@ -24,7 +24,7 @@ class ActionFlow:
     def do(self, action: type[Action]):
         name = action.__name__
         index = self.indices.get(name)
-        assert index is not None
+        assert index is not None, "Action '%s' is not registered" % name
         
         if self.on[index]: raise Unavailable(name)
         if self.on[index] is None: raise NotAllowed(name)
@@ -40,7 +40,7 @@ class ActionFlow:
     def index(self, action: type[Action]) -> int:
         name = action.__name__
         index = self.indices.get(name)
-        assert index is not None
+        assert index is not None, "Action '%s' is not registered" % name
         return index
     
     def allow(self, action: type[Action], value=True):
diff --git a/src/common/timer.py b/src/common/timer.py
index f006d73..e7bc1a7 100644
--- a/src/common/timer.py
+++ b/src/common/timer.py
@@ -14,9 +14,9 @@ class Timer:
         self.checkpoint = seconds
 
     def pause(self):
-        assert self.checkpoint is not None
+        assert self.checkpoint is not None, "Uninitialized"
         self.accumulator = self.delta()
 
     def delta(self):
-        assert self.checkpoint is not None
+        assert self.checkpoint is not None, "Uninitialized"
         return floor(time()) - self.checkpoint + self.accumulator