diff --git a/.gitattributes b/.gitattributes
index 8040b73f18..c0f363627b 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -13237,6 +13237,7 @@ tests/webtbs/tw2378.pp svneol=native#text/plain
 tests/webtbs/tw23819.pp -text svneol=native#text/plain
 tests/webtbs/tw2382.pp svneol=native#text/plain
 tests/webtbs/tw2388.pp svneol=native#text/plain
+tests/webtbs/tw23962.pp svneol=native#text/plain
 tests/webtbs/tw2397.pp svneol=native#text/plain
 tests/webtbs/tw2409.pp svneol=native#text/plain
 tests/webtbs/tw2421.pp svneol=native#text/plain
diff --git a/compiler/x86/aasmcpu.pas b/compiler/x86/aasmcpu.pas
index c63538de0b..77f15162a1 100644
--- a/compiler/x86/aasmcpu.pas
+++ b/compiler/x86/aasmcpu.pas
@@ -2892,6 +2892,7 @@ implementation
                 result:=taicpu.op_ref_reg(A_MOVSD,reg2opsize(r),ref,r);
               R_SUBMMS:
                 result:=taicpu.op_ref_reg(A_MOVSS,reg2opsize(r),ref,r);
+              R_SUBQ,
               R_SUBMMWHOLE:
                 result:=taicpu.op_ref_reg(A_MOVQ,S_NO,ref,r);
               else
@@ -2928,6 +2929,7 @@ implementation
                 result:=taicpu.op_reg_ref(A_MOVSD,reg2opsize(r),r,ref);
               R_SUBMMS:
                 result:=taicpu.op_reg_ref(A_MOVSS,reg2opsize(r),r,ref);
+              R_SUBQ,
               R_SUBMMWHOLE:
                 result:=taicpu.op_reg_ref(A_MOVQ,S_NO,r,ref);
               else
diff --git a/compiler/x86/cgx86.pas b/compiler/x86/cgx86.pas
index 6991924612..5d02763c28 100644
--- a/compiler/x86/cgx86.pas
+++ b/compiler/x86/cgx86.pas
@@ -206,7 +206,8 @@ unit cgx86;
             result:=rg[R_MMREGISTER].getregister(list,R_SUBMMD);
           OS_F32:
             result:=rg[R_MMREGISTER].getregister(list,R_SUBMMS);
-          OS_M64,
+          OS_M64:
+            result:=rg[R_MMREGISTER].getregister(list,R_SUBQ);
           OS_M128:
             result:=rg[R_MMREGISTER].getregister(list,R_SUBMMWHOLE);
           else
diff --git a/compiler/x86_64/cpupara.pas b/compiler/x86_64/cpupara.pas
index 20b4b5f1b4..f4b34f17ff 100644
--- a/compiler/x86_64/cpupara.pas
+++ b/compiler/x86_64/cpupara.pas
@@ -925,7 +925,7 @@ unit cpupara;
                           end;
                         else
                           begin
-                            setsubreg(paraloc^.register,R_SUBMMWHOLE);
+                            setsubreg(paraloc^.register,R_SUBQ);
                             paraloc^.size:=OS_M64;
                           end;
                       end;
@@ -1121,7 +1121,7 @@ unit cpupara;
                               end;
                             else
                               begin
-                                subreg:=R_SUBMMWHOLE;
+                                subreg:=R_SUBQ;
                                 paraloc^.size:=OS_M64;
                               end;
                           end;
diff --git a/tests/webtbs/tw23962.pp b/tests/webtbs/tw23962.pp
new file mode 100644
index 0000000000..33080610ea
--- /dev/null
+++ b/tests/webtbs/tw23962.pp
@@ -0,0 +1,46 @@
+{$MODE ObjFpc}
+
+uses classes;
+
+type
+
+TVector3 = packed record
+  X, Y, Z: Single;
+end;
+
+TClassA = class
+protected
+  fVector: TVector3;
+public
+  procedure SetVector(AVector: TVector3); virtual; abstract;
+end;
+
+{ TClassB }
+
+TClassB = class(TClassA)
+public
+  procedure SetVector(AVector: TVector3); override;
+end;
+
+{ TClassB }
+
+procedure TClassB.SetVector(AVector: TVector3);
+begin
+  writeln('TClassB: ',AVector.X,',',AVector.Y,',',AVector.Z);
+  fVector:=AVector;
+end;
+
+var
+  MyVector: TVector3;
+  MyClassB: TClassB;
+begin
+  MyVector.X:=0;
+  MyVector.Y:=0;
+  MyVector.Z:=3;
+  MyClassB:=TClassB.Create;
+  MyClassB.SetVector(MyVector);
+  if (MyClassB.fvector.x<>0) or
+     (MyClassB.fvector.y<>0) or
+     (MyClassB.fvector.z<>3) then
+    halt(1);
+end.