diff --git a/llvm/lib/ObjectYAML/MachOEmitter.cpp b/llvm/lib/ObjectYAML/MachOEmitter.cpp
--- a/llvm/lib/ObjectYAML/MachOEmitter.cpp
+++ b/llvm/lib/ObjectYAML/MachOEmitter.cpp
@@ -183,6 +183,30 @@
   return writePayloadString(LC, OS);
 }
 
+template <>
+size_t writeLoadCommandData<MachO::sub_framework_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_umbrella_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_client_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
+template <>
+size_t writeLoadCommandData<MachO::sub_library_command>(
+    MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
+  return writePayloadString(LC, OS);
+}
+
 template <>
 size_t writeLoadCommandData<MachO::build_version_command>(
     MachOYAML::LoadCommand &LC, raw_ostream &OS, bool IsLittleEndian) {
diff --git a/llvm/lib/ObjectYAML/MachOYAML.cpp b/llvm/lib/ObjectYAML/MachOYAML.cpp
--- a/llvm/lib/ObjectYAML/MachOYAML.cpp
+++ b/llvm/lib/ObjectYAML/MachOYAML.cpp
@@ -233,6 +233,30 @@
   IO.mapOptional("Content", LoadCommand.Content);
 }
 
+template <>
+void mapLoadCommandData<MachO::sub_framework_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_umbrella_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_client_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
+template <>
+void mapLoadCommandData<MachO::sub_library_command>(
+    IO &IO, MachOYAML::LoadCommand &LoadCommand) {
+  IO.mapOptional("Content", LoadCommand.Content);
+}
+
 template <>
 void mapLoadCommandData<MachO::build_version_command>(
     IO &IO, MachOYAML::LoadCommand &LoadCommand) {
diff --git a/llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test b/llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/MachO/sub-load-commands.test
@@ -0,0 +1,56 @@
+## This test verifies that llvm-objcopy correctly ignores the LC_SUB_* load
+## commands.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-objcopy %t %t2
+# RUN: cmp %t %t2
+# RUN: llvm-objdump --macho --private-headers %t2 | FileCheck %s
+
+--- !mach-o
+FileHeader:
+  magic:      0xFEEDFACF
+  cputype:    0x01000007
+  cpusubtype: 0x80000003
+  filetype:   0x00000002
+  ncmds:      4
+  sizeofcmds: 72
+  flags:      0x00200085
+  reserved:   0x00000000
+LoadCommands:
+  - cmd:          LC_SUB_FRAMEWORK
+    cmdsize:      16
+    umbrella:     12
+    Content:      'Bar'
+    ZeroPadBytes: 1
+  - cmd:          LC_SUB_UMBRELLA
+    cmdsize:      16
+    sub_umbrella: 12
+    Content:      'Foo'
+    ZeroPadBytes: 1
+  - cmd:          LC_SUB_LIBRARY
+    cmdsize:      24
+    sub_library:  12
+    Content:      'libfoo'
+    ZeroPadBytes: 6
+  - cmd:          LC_SUB_CLIENT
+    cmdsize:      16
+    client:       12
+    Content:      'bar'
+    ZeroPadBytes: 1
+
+# CHECK: Load command 0
+# CHECK:           cmd LC_SUB_FRAMEWORK
+# CHECK:       cmdsize 16
+# CHECK:      umbrella Bar (offset 12)
+# CHECK: Load command 1
+# CHECK:           cmd LC_SUB_UMBRELLA
+# CHECK:       cmdsize 16
+# CHECK:  sub_umbrella Foo (offset 12)
+# CHECK: Load command 2
+# CHECK:           cmd LC_SUB_LIBRARY
+# CHECK:       cmdsize 24
+# CHECK:   sub_library libfoo (offset 12)
+# CHECK: Load command 3
+# CHECK:           cmd LC_SUB_CLIENT
+# CHECK:       cmdsize 16
+# CHECK:        client bar (offset 12)
diff --git a/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp b/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp
--- a/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp
+++ b/llvm/tools/llvm-objcopy/MachO/MachOLayoutBuilder.cpp
@@ -380,6 +380,10 @@
     case MachO::LC_SOURCE_VERSION:
     case MachO::LC_THREAD:
     case MachO::LC_UNIXTHREAD:
+    case MachO::LC_SUB_FRAMEWORK:
+    case MachO::LC_SUB_UMBRELLA:
+    case MachO::LC_SUB_CLIENT:
+    case MachO::LC_SUB_LIBRARY:
       // Nothing to update.
       break;
     default: