diff --git a/.gitattributes b/.gitattributes
index a6f6840991..bf33be9003 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -10646,6 +10646,7 @@ tests/webtbs/tw1592.pp svneol=native#text/plain
 tests/webtbs/tw15930.pp svneol=native#text/plain
 tests/webtbs/tw16004.pp svneol=native#text/plain
 tests/webtbs/tw16018.pp svneol=native#text/plain
+tests/webtbs/tw16034.pp svneol=native#text/plain
 tests/webtbs/tw16040.pp svneol=native#text/plain
 tests/webtbs/tw16065.pp svneol=native#text/pascal
 tests/webtbs/tw16083.pp svneol=native#text/plain
diff --git a/compiler/symdef.pas b/compiler/symdef.pas
index 554b1fa27a..63b2c58233 100644
--- a/compiler/symdef.pas
+++ b/compiler/symdef.pas
@@ -4421,12 +4421,14 @@ implementation
                  tObjectSymtable(symtable).datasize:=align(tObjectSymtable(symtable).datasize,sizeof(pint));
                  tObjectSymtable(symtable).alignrecord(tObjectSymtable(symtable).datasize,sizeof(pint));
                end;
-
-             vmt_offset:=tObjectSymtable(symtable).datasize;
              vs:=tfieldvarsym.create('_vptr$'+objname^,vs_value,voidpointertype,[]);
              hidesym(vs);
              tObjectSymtable(symtable).insert(vs);
              tObjectSymtable(symtable).addfield(vs,vis_hidden);
+             if (tObjectSymtable(symtable).usefieldalignment<>bit_alignment) then
+               vmt_offset:=vs.fieldoffset
+             else
+               vmt_offset:=vs.fieldoffset div 8;
              include(objectoptions,oo_has_vmt);
           end;
      end;
diff --git a/tests/webtbs/tw16034.pp b/tests/webtbs/tw16034.pp
new file mode 100644
index 0000000000..3bee77feb0
--- /dev/null
+++ b/tests/webtbs/tw16034.pp
@@ -0,0 +1,160 @@
+program Hello;
+
+{$ifdef fpc}
+{$mode delphi}
+{$endif}
+
+{$APPTYPE CONSOLE}
+{$O-}
+
+type
+  ptr = pointer;
+  Int = ptrint;
+  pPtr = ^ptr;
+  UInt = ptruint;
+  Bool = Boolean;
+
+  // Object woth VMT at offset 0.
+  TObj0 =
+    object
+      Constructor Init;
+      Function Value(p: UInt): UInt; Virtual;
+    enD;
+
+  // Object with VMT at offset 0, and size = 5.
+  TObj1 =
+    object (TObj0)
+      f1: Byte; // UInt;
+
+      Constructor Init;
+      Function Value(p: UInt): UInt; Virtual;
+    enD;
+
+  // Object with VMT at offset 0, but size = 8. (???)
+  TObj2 =
+    object
+      f1{, f2, f3, f4}: Byte; // UInt;
+
+      Constructor Init;
+      Function Value(p: UInt): UInt; Virtual;
+    enD;
+
+{ Implmentation }
+
+Constructor TObj0.Init;
+begin
+enD;
+
+Function TObj0.Value(p: UInt): UInt;
+begin
+  Result := 0;
+enD;
+
+Constructor TObj1.Init;
+begin
+enD;
+
+Function TObj1.Value(p: UInt): UInt;
+begin
+  Result := 0;
+enD;
+
+Constructor TObj2.Init;
+begin
+enD;
+
+Function TObj2.Value(p: UInt): UInt;
+begin
+  Result := 0;
+enD;
+
+{ Low Level VMT Routines }
+
+type
+  pObjVMT = ^TObjVMT;
+  TObjVMT =
+    record
+      fInstanceSize: UInt;
+      fInstanceSize2: Int;
+      fParent: pObjVMT;
+    enD;
+
+Function GetInstanceSize(AVMT: pObjVMT): UInt;
+begin
+  Result := AVMT.fInstanceSize;
+enD;
+
+Function GetVMTPtrOffset(AVMT: pObjVMT): UInt;
+begin
+  if (AVMT.fParent = nil) then
+    Result := GetInstanceSize(AVMT) - SizeOf(ptr) else
+    Result := GetVMTPtrOffset(AVMT.fParent);
+enD;
+
+Function SetVMT(Obj: ptr; AVMT: ptr): Bool;
+begin
+  Result := (AVMT <> nil);
+
+  if (Result) then
+    pPtr(UInt(Obj) + GetVMTPtrOffset(AVMT))^ := AVMT;
+enD;
+
+
+{ Main }
+
+var
+  O0: TObj0;
+  O1: TObj1;
+  O2: TObj2;
+
+  s0, s1, s2: UInt;
+  v0, v1, v2: ptr;
+  cn0, cn1, cn2: ptr;
+
+begin
+  // VMT Pointers
+  v0 := TypeOf(TObj0);
+  v1 := TypeOf(TObj1);
+  v2 := TypeOf(TObj2);
+
+  // Object sizes
+  s0 := SizeOf(TObj0); // = 4
+  s1 := SizeOf(TObj1); // = 5
+  s2 := SizeOf(TObj2); // = 8 (???)
+  writeln(s0);
+  writeln(s1);
+  writeln(s2);
+
+  // Method pointers
+  cn0 := @TObj0.Value;
+  cn1 := @TObj1.Value;
+  cn2 := @TObj2.Value;
+
+  // VMT offsets (use in watches - need in program!)
+// Int(@o0._vptr$) - Int(@o0)     = 0
+// Int(@o1._vptr$) - Int(@o1)     = 0
+// Int(@o2._vptr$) - Int(@o2)     = 1 (???)
+
+{
+  // Constructors - skipping
+  O0.Init;
+  O1.Init;
+  O2.Init;
+}
+
+  // Store VMT (emulate constructor)
+  SetVMT(@O0, TypeOf(TObj0));
+  SetVMT(@O1, TypeOf(TObj1));
+  SetVMT(@O2, TypeOf(TObj2));
+
+  // Call Virtual Functions
+  O2.f1 := O0.Value(0);
+  O2.f1 := O1.Value(0);
+  O2.f1 := O2.Value(0); {CRASHES !!!}
+  { SizeOf(TObj2) must be 5,
+  or ptr(Int(@o2._vptr$) - Int(@o2)) must be 4! }
+
+  // MessageBox will be displayed, if all was successfull
+  writeln(O2.f1, 'Hello, FPC uWorld!', 'Hello', 0);
+end.
+