diff --git a/distributed/worker.py b/distributed/worker.py
index 010a5477ca..d964b5073c 100644
--- a/distributed/worker.py
+++ b/distributed/worker.py
@@ -1538,7 +1538,10 @@ def add_task(
             if self.validate:
                 if who_has:
                     assert all(self.tasks[dep] in ts.dependencies for dep in who_has)
-                self.validate_state()
+                    assert all(self.tasks[dep.key] for dep in ts.dependencies)
+                    for dependency in ts.dependencies:
+                        self.validate_task(dependency)
+                    self.validate_task(ts)
         except Exception as e:
             logger.exception(e)
             if LOG_PDB:
@@ -2498,7 +2501,6 @@ async def ensure_computing(self):
                     continue
                 if self.meets_resource_constraints(key):
                     self.constrained.popleft()
-                    # FIXME: Should this be part of the transition step?
                     # Ensure task is deserialized prior to execution
                     try:
                         ts.runspec = await self._maybe_deserialize_task(ts)
@@ -2518,7 +2520,6 @@ async def ensure_computing(self):
                 elif ts.key in self.data:
                     self.transition(ts, "memory")
                 elif ts.state in READY:
-                    # FIXME: Should this be part of the transition step?
                     # Ensure task is deserialized prior to execution
                     try:
                         ts.runspec = await self._maybe_deserialize_task(ts)
@@ -2929,8 +2930,6 @@ def validate_task_flight(self, ts):
 
     def validate_task(self, ts):
         assert ts.key in self.tasks
-        for dependency in ts.dependencies:
-            dependency in self.tasks
         try:
             if ts.state == "memory":
                 self.validate_task_memory(ts)