diff --git a/members/models/activity.py b/members/models/activity.py
index afcf3a87..3549f42c 100644
--- a/members/models/activity.py
+++ b/members/models/activity.py
@@ -139,7 +139,27 @@ def clean(self):
                 f"Prisen er for lav. Denne type aktivitet skal koste mindst {min_amount} kr."
             )
 
-        if self.signup_closing > self.end_date:
+        if self.start_date is None:
+            errors["start_date"] = "Der skal angives en startdato for aktiviteten"
+
+        if self.end_date is None:
+            errors["end_date"] = "Der skal angives en slutdato for aktiviteten"
+
+        if self.signup_closing is None:
+            errors["signup_closing"] = "Der skal angives en dato for tilmeldingsfrist"
+
+        if (
+            (self.start_date is not None)
+            and (self.end_date is not None)
+            and (self.start_date > self.end_date)
+        ):
+            errors["signup_closing"] = "Startdato skal være før aktivitetens slutdato"
+
+        if (
+            (self.signup_closing is not None)
+            and (self.end_date is not None)
+            and (self.signup_closing > self.end_date)
+        ):
             errors["signup_closing"] = (
                 "Tilmeldingsfristen skal være før aktiviteten slutter"
             )