diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "ABIInfoImpl.h"
 #include "CGBlocks.h"
 #include "CGCXXABI.h"
 #include "CGDebugInfo.h"
@@ -701,6 +702,9 @@
         getOverlapForFieldInit(Field), AggValueSlot::IsNotZeroed,
         // Checks are made by the code that calls constructor.
         AggValueSlot::IsSanitizerChecked);
+    if (Field->hasAttr<NoUniqueAddressAttr>() &&
+        isEmptyRecord(getContext(), FieldType, true))
+      Slot = AggValueSlot::ignored();
     EmitAggExpr(Init, Slot);
     break;
   }
diff --git a/clang/test/CodeGenCXX/ctor-empty-nounique.cpp b/clang/test/CodeGenCXX/ctor-empty-nounique.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/CodeGenCXX/ctor-empty-nounique.cpp
@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -triple x86_64-windows-gnu -emit-llvm -o - %s | FileCheck %s
+
+// An empty struct is handled as a struct with a dummy i8, on all targets.
+// Most targets treat an empty struct return value as essentially void - but
+// some don't. (Currently, at least x86_64-windows-* and powerpc64le-* don't
+// treat it as void.)
+//
+// When intializing a struct with such a no_unique_address member, make sure we
+// don't write the dummy i8 into the struct where there's no space allocated for
+// it.
+//
+// This can only be tested with targets that don't treat empty struct returns as
+// void.
+
+struct S {};
+S f();
+struct Z {
+  int x;
+  [[no_unique_address]] S y;
+  Z();
+};
+Z::Z() : x(111), y(f()) {}
+
+// CHECK: define {{.*}} @_ZN1ZC2Ev
+
+// CHECK: %coerce = alloca %struct.S, align 1
+
+// CHECK: %call = call i8 @_Z1fv()
+// CHECK-NEXT: %coerce.dive = getelementptr inbounds %struct.S, ptr %coerce, i32 0, i32 0
+// CHECK-NEXT: store i8 %call, ptr %coerce.dive, align 1
+// CHECK-NEXT: ret void