diff --git a/assume/markets/base_market.py b/assume/markets/base_market.py
index 55abec25..e3cea45a 100644
--- a/assume/markets/base_market.py
+++ b/assume/markets/base_market.py
@@ -53,9 +53,9 @@ def validate_registration(
         Used to check if a participant is eligible to bid on this market
         """
 
-        # simple check that 1 MW can be bid at least
-        def requirement(unit):
-            return unit["unit_type"] != "power_plant" or abs(unit["max_power"]) >= 1
+        # simple check that 1 MW can be bid at least by  powerplants
+        def requirement(unit: dict):
+            return unit.get("unit_type") != "power_plant" or abs(unit["max_power"]) >= 1
 
         return all([requirement(info) for info in content["information"]])