diff --git a/NETGenerator/NETGenerator.cs b/NETGenerator/NETGenerator.cs
index 762bb8c39..c970d7cae 100644
--- a/NETGenerator/NETGenerator.cs
+++ b/NETGenerator/NETGenerator.cs
@@ -7612,7 +7612,7 @@ namespace PascalABCCompiler.NETGenerator
             {
                 if (value.obj.type.is_generic_parameter)
                     il.Emit(OpCodes.Constrained, helper.GetTypeReference(value.obj.type).tp);
-                else if (value.obj.conversion_type != null && value.obj.conversion_type.is_generic_parameter)
+                else if (value.obj.conversion_type != null && value.obj.conversion_type.is_generic_parameter && !value.obj.type.IsInterface)
                     il.Emit(OpCodes.Constrained, helper.GetTypeReference(value.obj.conversion_type).tp);
                 il.EmitCall(OpCodes.Callvirt, mi, null);
             }
diff --git a/TestSuite/generics68.pas b/TestSuite/generics68.pas
new file mode 100644
index 000000000..137729a96
--- /dev/null
+++ b/TestSuite/generics68.pas
@@ -0,0 +1,21 @@
+var i: integer;
+type
+  I1 = interface
+    procedure p1;
+  end;
+  
+  // Обязательно класс, не запись
+  t2 = class(I1)
+    public procedure p1;
+    begin
+      i := 1;
+    end;
+  end;
+  
+// Обязательно I1(o), (o as I1) работает без проблем
+procedure p0<T>(o: T) := I1(o).p1;
+
+begin
+  p0(new t2);
+  assert(i = 1);
+end.
\ No newline at end of file