diff --git a/pyinfra/server/server.py b/pyinfra/server/server.py
index acf4f0b..65d74c6 100644
--- a/pyinfra/server/server.py
+++ b/pyinfra/server/server.py
@@ -31,8 +31,8 @@ class Processor(abc.ABC):
     def submit(self, package, final):
         """Submit computation request to execution queue; computation is performed on demand.
 
-        Use for processor functions that are 1 -> n where n can take up a lot of memory, since
-        the"""
+        """
+
         self.execution_queue = chain(self.execution_queue, self.processor_fn(package, final=final))
 
     def compute_next(self):
@@ -61,6 +61,9 @@ def set_up_processing_server(process_fn):
     @app.route("/pickup", methods=["GET"])
     def pickup():
         result = processor.compute_next()
+        if not valid(result):
+            logger.error(f"Received invalid result: {result}")
+            result = Nothing
 
         if result is Nothing:
             resp = jsonify("No more items left")
@@ -73,3 +76,7 @@ def set_up_processing_server(process_fn):
         return resp
 
     return app
+
+
+def valid(result):
+    return isinstance(result, dict) or isinstance(result, Nothing)