diff --git a/.gitattributes b/.gitattributes
index 363ad12405..54147e0c12 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -12179,6 +12179,7 @@ tests/webtbs/tw2109.pp svneol=native#text/plain
 tests/webtbs/tw2110.pp svneol=native#text/plain
 tests/webtbs/tw21146.pp svneol=native#text/pascal
 tests/webtbs/tw21151.pp svneol=native#text/plain
+tests/webtbs/tw21177.pp svneol=native#text/plain
 tests/webtbs/tw2128.pp svneol=native#text/plain
 tests/webtbs/tw2129.pp svneol=native#text/plain
 tests/webtbs/tw2129b.pp svneol=native#text/plain
diff --git a/compiler/ncal.pas b/compiler/ncal.pas
index eeb6e26865..51d18209d5 100644
--- a/compiler/ncal.pas
+++ b/compiler/ncal.pas
@@ -2337,6 +2337,12 @@ implementation
                        para.left:=gen_procvar_context_tree
                      else
                        para.left:=gen_self_tree;
+                     { make sure that e.g. the self pointer of an advanced
+                       record does not become a regvar, because it's a vs_var
+                       parameter }
+                     if paramanager.push_addr_param(para.parasym.varspez,para.parasym.vardef,
+                         procdefinition.proccalloption) then
+                       make_not_regable(para.left,[ra_addr_regable]);
                    end
                 else
                  if vo_is_vmt in para.parasym.varoptions then
diff --git a/tests/webtbs/tw21177.pp b/tests/webtbs/tw21177.pp
new file mode 100644
index 0000000000..9f988a75b0
--- /dev/null
+++ b/tests/webtbs/tw21177.pp
@@ -0,0 +1,29 @@
+{$modeswitch ADVANCEDRECORDS}
+{$OPTIMIZATION REGVAR}
+program record_bug;
+
+type
+TColor = object
+  R : Byte;
+  function toDWord : DWord;
+end;
+
+function TColor.toDWord : DWord;
+begin
+  r:=4;
+  toDWord:=5;
+end;
+
+procedure Fill(Color: TColor);
+begin
+  Color.toDWord;
+  if color.r<>4 then
+    halt(1);
+end;
+
+var
+  c: TColor;
+begin
+  c.r:=1;
+  Fill(c);
+end.