diff --git a/.gitattributes b/.gitattributes
index 1d73c345e1..b36d3b1e1e 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -11003,6 +11003,7 @@ tests/webtbf/tw2046.pp svneol=native#text/plain
 tests/webtbf/tw2053.pp svneol=native#text/plain
 tests/webtbf/tw2053b.pp svneol=native#text/plain
 tests/webtbf/tw20580.pp svneol=native#text/pascal
+tests/webtbf/tw20661.pp svneol=native#text/plain
 tests/webtbf/tw2070.pp svneol=native#text/plain
 tests/webtbf/tw2128.pp svneol=native#text/plain
 tests/webtbf/tw2129.pp svneol=native#text/plain
diff --git a/compiler/ncal.pas b/compiler/ncal.pas
index d77b806304..8547ec592b 100644
--- a/compiler/ncal.pas
+++ b/compiler/ncal.pas
@@ -2971,6 +2971,14 @@ implementation
                   CGMessage(cg_e_cant_call_abstract_method);
               end;
 
+            { directly calling an interface/protocol/category/class helper
+              method via its type is not possible (always must be called via
+              the actual instance) }
+            if (methodpointer.nodetype=typen) and
+               (is_interface(methodpointer.resultdef) or
+                is_objc_protocol_or_category(methodpointer.resultdef)) then
+              CGMessage1(type_e_class_type_expected,methodpointer.resultdef.typename);
+
             { if an inherited con- or destructor should be  }
             { called in a con- or destructor then a warning }
             { will be made                                  }
diff --git a/tests/webtbf/tw20661.pp b/tests/webtbf/tw20661.pp
new file mode 100644
index 0000000000..6d433112a5
--- /dev/null
+++ b/tests/webtbf/tw20661.pp
@@ -0,0 +1,40 @@
+{ %fail }
+
+unit tw20661;
+
+{$mode objfpc}{$H+}
+
+interface
+
+const
+  PrescriptionStorageIntfId = '{C2F3C9F6-657C-4974-841A-4EBFF33B2180}';//'blik.prescriptionstorage';
+  DatasetProviderIntfId = '{B0B1501A-9266-48EA-B2E0-7EF23511D799}';
+
+type
+  IDatasetPool = interface
+    ['{F866EB5B-5B32-438E-918E-A56B031C73DA}']
+    procedure ReleaseDataset(Instance: pointer);
+  end;
+
+  { TBlikServices }
+
+  TBlikServices = class
+  public
+    procedure ReleaseDataset(Instance: pointer);
+  end;
+
+var
+  Services: TBlikServices;
+
+implementation
+
+{ TBlikServices }
+
+procedure TBlikServices.ReleaseDataset(Instance: pointer);
+begin
+  IDatasetPool.ReleaseDataset(Instance);
+end;
+
+end.
+
+