diff --git a/.gitattributes b/.gitattributes
index 2de1992b7d..bce3c63d0a 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -13404,6 +13404,7 @@ tests/webtbs/tw20995a.pp svneol=native#text/pascal
 tests/webtbs/tw20995b.pp svneol=native#text/pascal
 tests/webtbs/tw20996.pp svneol=native#text/pascal
 tests/webtbs/tw20998.pp svneol=native#text/pascal
+tests/webtbs/tw21015.pp svneol=native#text/pascal
 tests/webtbs/tw21029.pp svneol=native#text/plain
 tests/webtbs/tw21044.pp svneol=native#text/pascal
 tests/webtbs/tw21051.pp svneol=native#text/pascal
@@ -14356,6 +14357,7 @@ tests/webtbs/uw20909a.pas svneol=native#text/pascal
 tests/webtbs/uw20909b.pas svneol=native#text/pascal
 tests/webtbs/uw20940.pp svneol=native#text/pascal
 tests/webtbs/uw20996.pp svneol=native#text/pascal
+tests/webtbs/uw21015.pp svneol=native#text/pascal
 tests/webtbs/uw21538.pp svneol=native#text/pascal
 tests/webtbs/uw21808a.pp svneol=native#text/plain
 tests/webtbs/uw21808b.pp svneol=native#text/plain
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 90b89a0a80..778d13dc18 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -1087,7 +1087,7 @@ implementation
       { target }
       systems,paramgr,
       { symtable }
-      symsym,symtable,defutil,objcdef,
+      symsym,symtable,defutil,objcdef,defcmp,
 {$ifdef jvm}
       jvmdef,
 {$endif}
@@ -1150,7 +1150,7 @@ implementation
           that concatenation shouldn't be converted to defaultsystemcodepage
           if all strings have the same type }
         result:=tstringdef(def).encoding;
-        if result=CP_NONE then
+        if result=globals.CP_NONE then
           result:=0
       end;
 
@@ -6488,7 +6488,7 @@ implementation
         for i:=0 to ImplementedInterfaces.Count-1 do
           begin
             ImplIntf:=TImplementedInterface(ImplementedInterfaces[i]);
-            if ImplIntf.intfdef=aintfdef then
+            if equal_defs(implintf.intfdef,aintfdef) then
               begin
                 result:=ImplIntf;
                 exit;
diff --git a/tests/webtbs/tw21015.pp b/tests/webtbs/tw21015.pp
new file mode 100644
index 0000000000..70343667cc
--- /dev/null
+++ b/tests/webtbs/tw21015.pp
@@ -0,0 +1,14 @@
+{ %NORUN }
+
+program tw21015;
+
+{$mode delphi}
+
+uses
+  uw21015;
+
+var
+  x: IIntTest;
+begin
+  x := TGenImpl<Integer>.Create;
+end.
\ No newline at end of file
diff --git a/tests/webtbs/uw21015.pp b/tests/webtbs/uw21015.pp
new file mode 100644
index 0000000000..9033033839
--- /dev/null
+++ b/tests/webtbs/uw21015.pp
@@ -0,0 +1,17 @@
+unit uw21015;
+
+{$mode delphi}
+
+interface
+
+type
+  ITest<T> = interface
+  end;
+
+  TGenImpl<T> = class (TInterfacedObject,ITest<T>)
+  end;
+
+  IIntTest = Itest<Integer>;
+implementation
+
+end. 
\ No newline at end of file