diff --git a/src/google/protobuf/compiler/cpp/message.cc b/src/google/protobuf/compiler/cpp/message.cc
index e9e0ae2e37..a519ee924b 100644
--- a/src/google/protobuf/compiler/cpp/message.cc
+++ b/src/google/protobuf/compiler/cpp/message.cc
@@ -3744,11 +3744,14 @@ void MessageGenerator::GenerateMergeFrom(io::Printer* p) {
 
   if (!HasDescriptorMethods(descriptor_->file(), options_)) {
     // Generate CheckTypeAndMergeFrom().
-    format(
-        "void $classname$::CheckTypeAndMergeFrom(\n"
-        "    const ::$proto_ns$::MessageLite& from) {\n"
-        "  MergeFrom(::$proto_ns$::DownCastToGenerated<$classname$>(from));\n"
-        "}\n");
+    // We pass `*this` instead of `default_instance()` to allow for ICF.
+    p->Emit(R"cc(
+      void $classname$::CheckTypeAndMergeFrom(
+          const ::$proto_ns$::MessageLite& from) {
+        $pbi$::AssertDownCast(from, *this);
+        MergeFrom(static_cast<const $classname$&>(from));
+      }
+    )cc");
   }
 }
 
diff --git a/src/google/protobuf/message_lite.h b/src/google/protobuf/message_lite.h
index 990b92292e..4c3b7ea7d5 100644
--- a/src/google/protobuf/message_lite.h
+++ b/src/google/protobuf/message_lite.h
@@ -863,6 +863,11 @@ T* OnShutdownDelete(T* p) {
   return p;
 }
 
+inline void AssertDownCast(const MessageLite& from, const MessageLite& to) {
+  ABSL_DCHECK(internal::TypeId::Get(from) == internal::TypeId::Get(to))
+      << "Cannot downcast " << from.GetTypeName() << " to " << to.GetTypeName();
+}
+
 }  // namespace internal
 
 std::string ShortFormat(const MessageLite& message_lite);