Index: clang/lib/CodeGen/CGVTables.cpp
===================================================================
--- clang/lib/CodeGen/CGVTables.cpp
+++ clang/lib/CodeGen/CGVTables.cpp
@@ -1174,7 +1174,17 @@
 
   // Otherwise, if we don't have a definition of the key function, the
   // vtable must be defined somewhere else.
-  return !keyFunction->hasBody();
+  if (!keyFunction->hasBody())
+    return true;
+
+  // If the class comes from another translation unit, the vtable must be
+  // defined there.
+  if (auto *M = RD->getOwningModule();
+      M && M->getTopLevelModule()->isModulePurview() &&
+      M->getTopLevelModule() != CGM.getContext().getNamedModuleForCodeGen())
+    return true;
+
+  return false;
 }
 
 /// Given that we're currently at the end of the translation unit, and
Index: clang/test/CodeGenCXX/modules-vtable.cppm
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/modules-vtable.cppm
@@ -0,0 +1,58 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+// RUN: cd %t
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 -emit-module-interface \
+// RUN:     %t/Base.cppm -o %t/Base.pcm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 -emit-module-interface \
+// RUN:     %t/Sub.cppm -o %t/Sub.pcm -fmodule-file=Mod:Base=%t/Base.pcm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 -emit-module-interface \
+// RUN:     %t/Mod.cppm -o %t/Mod.pcm -fmodule-file=Mod:Base=%t/Base.pcm \
+// RUN:     -fmodule-file=Mod:Sub=%t/Sub.pcm
+//
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 %t/Base.pcm \
+// RUN:     -emit-llvm -o - | FileCheck %t/Base.cppm
+// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++20 -fmodule-file=Mod=%t/Mod.pcm \
+// RUN:     %t/Use.cpp  -emit-llvm -o - | FileCheck %t/Use.cpp
+
+//--- Base.cppm
+export module Mod:Base;
+export class Base {
+public:
+    Base();
+    virtual ~Base();
+};
+Base::Base() {}
+Base::~Base() {}
+
+// CHECK: @_ZTVW3Mod4Base = unnamed_addr constant
+// CHECK: @_ZTSW3Mod4Base = constant
+// CHECK: @_ZTIW3Mod4Base = constant
+
+//--- Sub.cppm
+export module Mod:Sub;
+import :Base;
+export class Sub : public Base {
+
+};
+
+// CHECK
+
+//--- Mod.cppm
+export module Mod;
+export import :Base;
+export import :Sub;
+
+//--- Use.cpp
+import Mod;
+int use() {
+    Base *b = new Sub();
+}
+
+// CHECK-NOT: @_ZTSW3Mod4Base = constant
+// CHECK-NOT: @_ZTIW3Mod4Base = constant
+
+// CHECK-DAG: @_ZTVW3Mod3Sub = linkonce_odr unnamed_addr
+// CHECK-DAG: @_ZTSW3Mod3Sub = linkonce_odr
+// CHECK-DAG: @_ZTIW3Mod4Base = external constant ptr
+// CHECK-DAG: @_ZTIW3Mod3Sub = linkonce_odr