diff --git a/lld/MachO/InputFiles.cpp b/lld/MachO/InputFiles.cpp
--- a/lld/MachO/InputFiles.cpp
+++ b/lld/MachO/InputFiles.cpp
@@ -1558,6 +1558,7 @@
   case GlobalValue::DefaultVisibility:
     break;
   }
+  isPrivateExtern = isPrivateExtern || objSym.canBeOmittedFromSymbolTable();
 
   if (objSym.isCommon())
     return symtab->addCommon(name, &file, objSym.getCommonSize(),
diff --git a/lld/test/MachO/lto-internalize-unnamed-addr.ll b/lld/test/MachO/lto-internalize-unnamed-addr.ll
new file mode 100644
--- /dev/null
+++ b/lld/test/MachO/lto-internalize-unnamed-addr.ll
@@ -0,0 +1,75 @@
+; REQUIRES: x86
+; RUN: rm -rf %t; split-file %s %t
+;; This test covers both FullLTO and ThinLTO code paths because we have observed
+;; (unexpected) differences between the two.
+; RUN: llvm-as %t/test.ll -o %t/test.o
+; RUN: llvm-as %t/test2.ll -o %t/test2.o
+; RUN: opt -module-summary %t/test.ll -o %t/test.thinlto.o
+; RUN: opt -module-summary %t/test2.ll -o %t/test2.thinlto.o
+
+; RUN: %lld -lSystem %t/test.o %t/test2.o -o %t/test
+; RUN: llvm-nm -m %t/test | FileCheck %s --check-prefix=LTO
+
+; RUN: %lld -lSystem -dylib %t/test.o %t/test2.o -o %t/test.dylib
+; RUN: llvm-nm -m %t/test.dylib | FileCheck %s --check-prefix=LTO-DYLIB
+
+; RUN: %lld -lSystem %t/test.thinlto.o %t/test2.o -o %t/test.thinlto
+; RUN: llvm-nm -m %t/test.thinlto | FileCheck %s --check-prefix=THINLTO
+
+; RUN: %lld -lSystem -dylib %t/test.thinlto.o %t/test2.o -o %t/test.thinlto.dylib
+; RUN: llvm-nm -m %t/test.thinlto.dylib | FileCheck %s --check-prefix=THINLTO
+
+; LTO-DAG: (__DATA,__data) non-external _global_unnamed
+; LTO-DAG: (__DATA,__data) non-external _local_unnamed
+;; LD64 marks this with (was a private external). IMO both LD64 and LLD should
+;; mark all the other internalized symbols with (was a private external).
+; LTO-DAG: (__TEXT,__const) non-external _local_unnamed_always_const
+; LTO-DAG: (__TEXT,__const) non-external _local_unnamed_const
+;; LD64 doesn't internalize this -- it emits it as a weak external -- which I
+;; think is a missed optimization on its end.
+; LTO-DAG: (__TEXT,__const) non-external _local_unnamed_sometimes_const
+
+;; The output here is largely identical to LD64's, except that the non-external
+;; symbols here are all marked as (was a private external) by LD64. LLD should
+;; follow suit.
+; LTO-DYLIB-DAG: (__DATA,__data) non-external _global_unnamed
+; LTO-DYLIB-DAG: (__DATA,__data) weak external _local_unnamed
+; LTO-DYLIB-DAG: (__TEXT,__const) non-external _local_unnamed_always_const
+; LTO-DYLIB-DAG: (__TEXT,__const) non-external _local_unnamed_const
+; LTO-DYLIB-DAG: (__TEXT,__const) weak external _local_unnamed_sometimes_const
+
+; THINLTO-DAG: (__DATA,__data) non-external (was a private external) _global_unnamed
+; THINLTO-DAG: (__DATA,__data) weak external _local_unnamed
+;; The next two symbols are rendered as non-external (was a private external)
+;; by LD64. This is a missed optimization on LLD's end.
+; THINLTO-DAG: (__TEXT,__const) weak external _local_unnamed_always_const
+; THINLTO-DAG: (__TEXT,__const) weak external _local_unnamed_const
+;; LD64 actually fails to link when the following symbol is included in the test
+;; input, instead producing this error:
+;; reference to bitcode symbol '_local_unnamed_sometimes_const' which LTO has not compiled in '_used' from /tmp/lto.o for architecture x86_64
+; THINLTO-DAG: (__TEXT,__const) weak external _local_unnamed_sometimes_const
+
+;--- test.ll
+target triple = "x86_64-apple-darwin"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+@global_unnamed = linkonce_odr unnamed_addr global i8 42
+@local_unnamed_const = linkonce_odr local_unnamed_addr constant i8 42
+@local_unnamed_always_const = linkonce_odr local_unnamed_addr constant i8 42
+@local_unnamed_sometimes_const = linkonce_odr local_unnamed_addr constant i8 42
+@local_unnamed = linkonce_odr local_unnamed_addr global i8 42
+@used = hidden constant [5 x i8*] [i8* @global_unnamed, i8* @local_unnamed,
+  i8* @local_unnamed_const, i8* @local_unnamed_always_const,
+  i8* @local_unnamed_sometimes_const]
+@llvm.used = appending global [1 x [5 x i8*]*] [[5 x i8*]* @used]
+
+define void @main() {
+  ret void
+}
+
+;--- test2.ll
+target triple = "x86_64-apple-darwin"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+
+@local_unnamed_always_const = linkonce_odr local_unnamed_addr constant i8 42
+@local_unnamed_sometimes_const = linkonce_odr local_unnamed_addr global i8 42