Index: llvm/lib/TextAPI/MachO/TextStubCommon.cpp
===================================================================
--- llvm/lib/TextAPI/MachO/TextStubCommon.cpp
+++ llvm/lib/TextAPI/MachO/TextStubCommon.cpp
@@ -152,8 +152,14 @@
   return QuotingType::None;
 }
 
-void ScalarTraits<SwiftVersion>::output(const SwiftVersion &Value, void *,
+void ScalarTraits<SwiftVersion>::output(const SwiftVersion &Value, void *IO,
                                         raw_ostream &OS) {
+  const auto *Ctx = reinterpret_cast<TextAPIContext *>(IO);
+  if (Ctx->FileKind == FileType::TBD_V4) {
+    OS << (unsigned)Value;
+    return;
+  }
+
   switch (Value) {
   case 1:
     OS << "1.0";
Index: llvm/unittests/TextAPI/TextStubV4Tests.cpp
===================================================================
--- llvm/unittests/TextAPI/TextStubV4Tests.cpp
+++ llvm/unittests/TextAPI/TextStubV4Tests.cpp
@@ -504,7 +504,11 @@
   EXPECT_EQ(FileType::TBD_V4, File->getFileType());
   EXPECT_EQ(1U, File->getSwiftABIVersion());
 
-  // No writer test because we emit "swift-abi-version:1.0".
+  SmallString<4096> Buffer;
+  raw_svector_ostream OS(Buffer);
+  auto WriteResult = TextAPIWriter::writeToStream(OS, *File);
+  EXPECT_TRUE(!WriteResult);
+  EXPECT_EQ(stripWhitespace(tbd_swift_1), stripWhitespace(Buffer.c_str()));
 }
 
 TEST(TBDv4, Swift_2) {
@@ -521,7 +525,11 @@
   EXPECT_EQ(FileType::TBD_V4, File->getFileType());
   EXPECT_EQ(2U, File->getSwiftABIVersion());
 
-  // No writer test because we emit "swift-abi-version:2.0".
+  SmallString<4096> Buffer;
+  raw_svector_ostream OS(Buffer);
+  auto WriteResult = TextAPIWriter::writeToStream(OS, *File);
+  EXPECT_TRUE(!WriteResult);
+  EXPECT_EQ(stripWhitespace(tbd_v4_swift_2), stripWhitespace(Buffer.c_str()));
 }
 
 TEST(TBDv4, Swift_5) {