diff --git a/.gitattributes b/.gitattributes
index e0759023d2..8aae5d880f 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -16071,6 +16071,7 @@ tests/webtbf/tw3583.pp svneol=native#text/plain
 tests/webtbf/tw35866.pp svneol=native#text/pascal
 tests/webtbf/tw35981.pp svneol=native#text/pascal
 tests/webtbf/tw36114.pp svneol=native#text/pascal
+tests/webtbf/tw36223.pp svneol=native#text/pascal
 tests/webtbf/tw3626.pp svneol=native#text/plain
 tests/webtbf/tw3631.pp svneol=native#text/plain
 tests/webtbf/tw3643.pp svneol=native#text/plain
diff --git a/compiler/symtable.pas b/compiler/symtable.pas
index 77eb5034fc..22269a68f4 100644
--- a/compiler/symtable.pas
+++ b/compiler/symtable.pas
@@ -3916,8 +3916,17 @@ implementation
               exit;
           end;
         { now search all helpers using the extendeddef as the starting point }
-        if m_multi_helpers in current_settings.modeswitches then
-          result:=search_best_objectpascal_helper(s,classh.extendeddef,contextclassh,srsym,srsymtable);
+        if (m_multi_helpers in current_settings.modeswitches) and
+            (
+              (current_structdef<>classh) or
+              assigned(classh.extendeddef)
+            ) then
+          begin
+            { this is only allowed if classh is currently parsed }
+            if not assigned(classh.extendeddef) then
+              internalerror(2019110101);
+            result:=search_best_objectpascal_helper(s,classh.extendeddef,contextclassh,srsym,srsymtable);
+          end;
       end;
 
     function search_specific_assignment_operator(assignment_type:ttoken;from_def,to_def:Tdef):Tprocdef;
diff --git a/tests/webtbf/tw36223.pp b/tests/webtbf/tw36223.pp
new file mode 100644
index 0000000000..d59ae0c51d
--- /dev/null
+++ b/tests/webtbf/tw36223.pp
@@ -0,0 +1,18 @@
+{ %FAIL }
+
+{$mode objfpc}
+{$modeswitch multihelpers}
+
+unit tw36223;
+interface
+uses
+  SysUtils;
+
+type
+  // ERROR: Compilation raised exception internally
+  TMyHelper = class helper for TSomeObject
+  end;
+
+implementation
+
+end.