diff --git a/lib/CodeGen/AsmPrinter/DIEHash.cpp b/lib/CodeGen/AsmPrinter/DIEHash.cpp
index ff04ec7f2d7..201030f0ac5 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.cpp
+++ b/lib/CodeGen/AsmPrinter/DIEHash.cpp
@@ -380,10 +380,12 @@ void DIEHash::computeHash(const DIE &Die) {
 /// DWARF4 standard. It is an md5 hash of the flattened description of the DIE
 /// with the inclusion of the full CU and all top level CU entities.
 // TODO: Initialize the type chain at 0 instead of 1 for CU signatures.
-uint64_t DIEHash::computeCUSignature(const DIE &Die) {
+uint64_t DIEHash::computeCUSignature(StringRef DWOName, const DIE &Die) {
   Numbering.clear();
   Numbering[&Die] = 1;
 
+  if (!DWOName.empty())
+    Hash.update(DWOName);
   // Hash the DIE.
   computeHash(Die);
 
diff --git a/lib/CodeGen/AsmPrinter/DIEHash.h b/lib/CodeGen/AsmPrinter/DIEHash.h
index e2864b17fe2..29337ae38a9 100644
--- a/lib/CodeGen/AsmPrinter/DIEHash.h
+++ b/lib/CodeGen/AsmPrinter/DIEHash.h
@@ -36,7 +36,7 @@ public:
   DIEHash(AsmPrinter *A = nullptr) : AP(A) {}
 
   /// \brief Computes the CU signature.
-  uint64_t computeCUSignature(const DIE &Die);
+  uint64_t computeCUSignature(StringRef DWOName, const DIE &Die);
 
   /// \brief Computes the type signature.
   uint64_t computeTypeSignature(const DIE &Die);
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 06358c42cfe..bf27516e1cc 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -613,6 +613,13 @@ void DwarfDebug::finalizeModuleInfo() {
 
   finishVariableDefinitions();
 
+  // Include the DWO file name in the hash if there's more than one CU.
+  // This handles ThinLTO's situation where imported CUs may very easily be
+  // duplicate with the same CU partially imported into another ThinLTO unit.
+  StringRef DWOName;
+  if (CUMap.size() > 1)
+    DWOName = Asm->TM.Options.MCOptions.SplitDwarfFile;
+
   // Handle anything that needs to be done on a per-unit basis after
   // all other generation.
   for (const auto &P : CUMap) {
@@ -627,7 +634,8 @@ void DwarfDebug::finalizeModuleInfo() {
     auto *SkCU = TheCU.getSkeleton();
     if (useSplitDwarf()) {
       // Emit a unique identifier for this CU.
-      uint64_t ID = DIEHash(Asm).computeCUSignature(TheCU.getUnitDie());
+      uint64_t ID =
+          DIEHash(Asm).computeCUSignature(DWOName, TheCU.getUnitDie());
       TheCU.addUInt(TheCU.getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
                     dwarf::DW_FORM_data8, ID);
       SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
diff --git a/test/DebugInfo/X86/split-dwarf-multiple-cu-hash.ll b/test/DebugInfo/X86/split-dwarf-multiple-cu-hash.ll
new file mode 100644
index 00000000000..f801ade27bd
--- /dev/null
+++ b/test/DebugInfo/X86/split-dwarf-multiple-cu-hash.ll
@@ -0,0 +1,42 @@
+; RUN: %llc_dwarf -split-dwarf-file=foo.dwo  %s -filetype=obj -o %T/a.o
+; RUN: %llc_dwarf -split-dwarf-file=bar.dwo  %s -filetype=obj -o %T/b.o
+; RUN: llvm-dwarfdump -debug-dump=info %T/a.o %T/b.o | FileCheck %s
+
+; CHECK: dwo_id {{.*}}([[HASH:.*]])
+; CHECK-NOT: dwo_id {{.*}}([[HASH]])
+
+target triple = "x86_64-pc-linux"
+
+; Function Attrs: noinline nounwind uwtable
+define void @_Z1av() #0 !dbg !9 {
+entry:
+  ret void, !dbg !12
+}
+
+; Function Attrs: noinline nounwind uwtable
+define void @_Z1bv() #0 !dbg !13 {
+entry:
+  ret void, !dbg !14
+}
+
+attributes #0 = { noinline nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.dbg.cu = !{!0, !3}
+!llvm.ident = !{!5, !5}
+!llvm.module.flags = !{!6, !7, !8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 5.0.0 (trunk 304107) (llvm/trunk 304109)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "a.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!2 = !{}
+!3 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !4, producer: "clang version 5.0.0 (trunk 304107) (llvm/trunk 304109)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!4 = !DIFile(filename: "b.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!5 = !{!"clang version 5.0.0 (trunk 304107) (llvm/trunk 304109)"}
+!6 = !{i32 2, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = distinct !DISubprogram(name: "a", linkageName: "_Z1av", scope: !1, file: !1, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !0, variables: !2)
+!10 = !DISubroutineType(types: !11)
+!11 = !{null}
+!12 = !DILocation(line: 2, column: 1, scope: !9)
+!13 = distinct !DISubprogram(name: "b", linkageName: "_Z1bv", scope: !4, file: !4, line: 1, type: !10, isLocal: false, isDefinition: true, scopeLine: 1, flags: DIFlagPrototyped, isOptimized: false, unit: !3, variables: !2)
+!14 = !DILocation(line: 2, column: 1, scope: !13)