Index: lib/ReaderWriter/MachO/ArchHandler_x86_64.cpp
===================================================================
--- lib/ReaderWriter/MachO/ArchHandler_x86_64.cpp
+++ lib/ReaderWriter/MachO/ArchHandler_x86_64.cpp
@@ -60,7 +60,8 @@
   }
 
   bool isTLVAccess(const Reference &ref) const override {
-    assert(ref.kindNamespace() == Reference::KindNamespace::mach_o);
+    if (ref.kindNamespace() != Reference::KindNamespace::mach_o)
+      return false;
     assert(ref.kindArch() == Reference::KindArch::x86_64);
     return ref.kindValue() == ripRel32Tlv;
   }
Index: test/mach-o/tlv-refkind.yaml
===================================================================
--- /dev/null
+++ test/mach-o/tlv-refkind.yaml
@@ -0,0 +1,56 @@
+# RUN: lld -flavor darwin -arch x86_64  %s %p/Inputs/libSystem.yaml \
+# RUN: -o %t
+# RUN: llvm-nm -m -n %t | FileCheck %s
+#
+#
+# Test that x86_64 checking for TLV on local symbols properly accounts for
+# references not in the mach_o:: namespace. Specifically in this case,
+# all::layout_after references.
+#
+--- !mach-o
+arch:            x86_64
+file-type:       MH_OBJECT
+flags:           [  ]
+compat-version:  0.0
+current-version: 0.0
+has-UUID:        false
+OS:              unknown
+sections:
+  - segment:         __TEXT
+    section:         __text
+    type:            S_REGULAR
+    attributes:      [ S_ATTR_PURE_INSTRUCTIONS, S_ATTR_SOME_INSTRUCTIONS ]
+    address:         0x0000000000000000
+    content:         [ 0xC3 ]
+  - segment:         __DATA
+    section:         __data
+    type:            S_REGULAR
+    attributes:      [  ]
+    address:         0x0000000000000001
+    content:         [ 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00 ]
+local-symbols:
+  - name:            l.blah
+    type:            N_SECT
+    sect:            2
+    value:           0x0000000000000001
+  - name:            l.blaz
+    type:            N_SECT
+    sect:            2
+    value:           0x0000000000000005
+global-symbols:
+  - name:            _foo
+    type:            N_SECT
+    scope:           [ N_EXT ]
+    sect:            2
+    value:           0x0000000000000001
+  - name:            _main
+    type:            N_SECT
+    scope:           [ N_EXT ]
+    sect:            1
+    value:           0x0000000000000000
+page-size:       0x00000000
+...
+
+
+# CHECK: (undefined) external dyld_stub_binder (from libSystem)
+# CHECK-NEXT: external _main