diff --git a/netbox/dcim/forms/connections.py b/netbox/dcim/forms/connections.py
index 28677f977..854c5ebed 100644
--- a/netbox/dcim/forms/connections.py
+++ b/netbox/dcim/forms/connections.py
@@ -103,10 +103,4 @@ def get_cable_form(a_type, b_type):
             self.instance.a_terminations = self.cleaned_data['a_terminations']
             self.instance.b_terminations = self.cleaned_data['b_terminations']
 
-            if a_type == b_type and self.instance.a_terminations and self.instance.b_terminations:
-                if self.instance.a_terminations.intersection(self.instance.b_terminations):
-                    raise forms.ValidationError(
-                        _("A and B terminations cannot connect to the same object.")
-                    )
-
     return _CableForm
diff --git a/netbox/dcim/models/cables.py b/netbox/dcim/models/cables.py
index 751bca271..4283f74a8 100644
--- a/netbox/dcim/models/cables.py
+++ b/netbox/dcim/models/cables.py
@@ -180,6 +180,12 @@ class Cable(PrimaryModel):
                 if b_type not in COMPATIBLE_TERMINATION_TYPES.get(a_type):
                     raise ValidationError(f"Incompatible termination types: {a_type} and {b_type}")
 
+                if a_type == b_type:
+                    if (set(self.a_terminations) & set(self.b_terminations)):
+                        raise ValidationError(
+                            _("A and B terminations cannot connect to the same object.")
+                        )
+
             # Run clean() on any new CableTerminations
             for termination in self.a_terminations:
                 CableTermination(cable=self, cable_end='A', termination=termination).clean()