diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -640,6 +640,9 @@
                VTableHolder, TemplateParams, &Identifier, Discriminator,
                DataLocation, Associated, Allocated, Rank, Annotations);
 
+  if (CT->getTag() != Tag)
+    return nullptr;
+
   // Only mutate CT if it's a forward declaration and the new operands aren't.
   assert(CT->getRawIdentifier() == &Identifier && "Wrong ODR identifier?");
   if (!CT->isForwardDecl() || (Flags & DINode::FlagFwdDecl))
@@ -672,12 +675,16 @@
   if (!Context.isODRUniquingDebugTypes())
     return nullptr;
   auto *&CT = (*Context.pImpl->DITypeMap)[&Identifier];
-  if (!CT)
+  if (!CT) {
     CT = DICompositeType::getDistinct(
         Context, Tag, Name, File, Line, Scope, BaseType, SizeInBits,
         AlignInBits, OffsetInBits, Flags, Elements, RuntimeLang, VTableHolder,
         TemplateParams, &Identifier, Discriminator, DataLocation, Associated,
         Allocated, Rank, Annotations);
+  } else {
+    if (CT->getTag() != Tag)
+      return nullptr;
+  }
   return CT;
 }
 
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -549,6 +549,8 @@
   void verifyFunctionAttrs(FunctionType *FT, AttributeList Attrs,
                            const Value *V, bool IsIntrinsic);
   void verifyFunctionMetadata(ArrayRef<std::pair<unsigned, MDNode *>> MDs);
+  template <typename T>
+  void verifyODRTypeAsScopeOperand(const MDNode &MD, T * = nullptr);
 
   void visitConstantExprsRecursively(const Constant *EntryC);
   void visitConstantExpr(const ConstantExpr *CE);
@@ -839,6 +841,19 @@
   }
 }
 
+template <typename T>
+void Verifier::verifyODRTypeAsScopeOperand(const MDNode &MD, T *) {
+  if (isa<T>(MD)) {
+    if (auto *N = dyn_cast_or_null<DICompositeType>(cast<T>(MD).getScope()))
+      // Of all the supported tags for DICompositeType(see visitDICompositeType)
+      // we know that enum type cannot be a scope.
+      AssertDI(N->getTag() != dwarf::DW_TAG_enumeration_type,
+               "enum type is not a scope; check enum type ODR "
+               "violation",
+               N, &MD);
+  }
+}
+
 void Verifier::visitMDNode(const MDNode &MD, AreDebugLocsAllowed AllowLocs) {
   // Only visit each node once.  Metadata can be mutually recursive, so this
   // avoids infinite recursion here, as well as being an optimization.
@@ -848,6 +863,12 @@
   Assert(&MD.getContext() == &Context,
          "MDNode context does not match Module context!", &MD);
 
+  // Makes sure when a scope operand is a ODR type, the ODR type uniquing does
+  // not create invalid debug metadata.
+  // TODO: check that the non-ODR-type scope operand is valid.
+  verifyODRTypeAsScopeOperand<DIType>(MD);
+  verifyODRTypeAsScopeOperand<DILocalScope>(MD);
+
   switch (MD.getMetadataID()) {
   default:
     llvm_unreachable("Invalid MDNode subclass");
diff --git a/llvm/test/Linker/debug-info-bad-enum.ll b/llvm/test/Linker/debug-info-bad-enum.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Linker/debug-info-bad-enum.ll
@@ -0,0 +1,47 @@
+; Check that ODR type uniquing does not create invalid debug metadata.
+; RUN: split-file %s %t
+; RUN: llvm-link -S -o - %t/a.ll %t/b.ll 2>&1 | FileCheck %s
+
+; CHECK-DAG: distinct !DICompileUnit({{.*}}, enums: ![[ENUMLIST:[0-9]+]],
+; CHECK-DAG: ![[ENUMLIST]] = !{![[ENUM:[0-9]+]]}
+; CHECK-DAG: ![[ENUM]] = distinct !DICompositeType(tag: DW_TAG_enumeration_type, {{.*}}, identifier: "_ZTS5Stage"
+
+; CHECK-DAG: distinct !DICompileUnit({{.*}}, retainedTypes: ![[RETAIN:[0-9]+]],
+; CHECK-DAG: ![[RETAIN]] = !{![[VAR:[0-9]+]]}
+; CHECK-DAG: ![[CLASS:[0-9]+]] = distinct !DICompositeType(tag: DW_TAG_class_type, {{.*}}, identifier: "_ZTS5Stage"
+; CHECK-DAG: ![[VAR]] = !DIDerivedType(tag: DW_TAG_member, name: "Var", scope: ![[CLASS]],
+
+; CHECK-NOT: enum type is not a scope; check enum type ODR violation
+
+;--- a.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "a.cpp", directory: "file")
+!2 = !{!3}
+!3 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "Stage", file: !1, line: 3, baseType: !4, size: 32, elements: !5, identifier: "_ZTS5Stage")
+!4 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!5 = !{!6}
+!6 = !DIEnumerator(name: "A1", value: 0, isUnsigned: true)
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+
+
+;--- b.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!11}
+
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang", isOptimized: true, emissionKind: FullDebug, retainedTypes: !10, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "b.cpp", directory: "file")
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = !DIDerivedType(tag: DW_TAG_member, name: "Var", scope: !8, file: !3, line: 5, baseType: !5, flags: DIFlagStaticMember)
+!8 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "Stage", file: !3, line: 3, size: 64, flags: DIFlagTypePassByValue, elements: !9, identifier: "_ZTS5Stage")
+!9 = !{!6}
+!10 = !{!6}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
diff --git a/llvm/test/Verifier/dbg-invalid-enum-as-scope.ll b/llvm/test/Verifier/dbg-invalid-enum-as-scope.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Verifier/dbg-invalid-enum-as-scope.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as -disable-output <%s 2>&1 | FileCheck %s
+; CHECK: enum type is not a scope; check enum type ODR violation
+; CHECK: warning: ignoring invalid debug info
+
+!llvm.module.flags = !{!0}
+!0 = !{i32 2, !"Debug Info Version", i32 3}
+!llvm.dbg.cu = !{!1}
+!1 = distinct !DICompileUnit(language: DW_LANG_C99, file: !2, producer: "clang", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, retainedTypes: !13, enums: !3)
+!2 = !DIFile(filename: "file.c", directory: "dir")
+!3 = !{!4}
+!4 = distinct !DICompositeType(tag: DW_TAG_enumeration_type, name: "Stage", file: !2, line: 3, baseType: !10, size: 32, elements: !11, identifier: "_ZTS5Stage")
+!6 = !DIDerivedType(tag: DW_TAG_member, name: "Var", scope: !4, file: !2, line: 5, baseType: !10)
+!10 = !DIBasicType(name: "unsigned int", size: 32, encoding: DW_ATE_unsigned)
+!11 = !{!12}
+!12 = !DIEnumerator(name: "A1", value: 0, isUnsigned: true)
+!13 = !{!6}
diff --git a/llvm/unittests/IR/DebugTypeODRUniquingTest.cpp b/llvm/unittests/IR/DebugTypeODRUniquingTest.cpp
--- a/llvm/unittests/IR/DebugTypeODRUniquingTest.cpp
+++ b/llvm/unittests/IR/DebugTypeODRUniquingTest.cpp
@@ -81,38 +81,38 @@
   EXPECT_EQ(dwarf::DW_TAG_class_type, CT.getTag());
 
   // Update with another forward decl.  This should be a no-op.
-  EXPECT_EQ(&CT,
-            DICompositeType::buildODRType(
-                Context, UUID, dwarf::DW_TAG_structure_type, nullptr, nullptr,
-                0, nullptr, nullptr, 0, 0, 0, DINode::FlagFwdDecl, nullptr, 0,
-                nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                nullptr));
-  EXPECT_EQ(dwarf::DW_TAG_class_type, CT.getTag());
+  EXPECT_EQ(&CT, DICompositeType::buildODRType(
+                     Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr,
+                     0, nullptr, nullptr, 0, 0, 0, DINode::FlagFwdDecl, nullptr,
+                     0, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                     nullptr, nullptr));
+
+  EXPECT_FALSE(DICompositeType::buildODRType(
+      Context, UUID, dwarf::DW_TAG_structure_type, nullptr, nullptr, 0, nullptr,
+      nullptr, 0, 0, 0, DINode::FlagFwdDecl, nullptr, 0, nullptr, nullptr,
+      nullptr, nullptr, nullptr, nullptr, nullptr, nullptr));
 
   // Update with a definition.  This time we should see a change.
-  EXPECT_EQ(&CT,
-            DICompositeType::buildODRType(
-                Context, UUID, dwarf::DW_TAG_structure_type, nullptr, nullptr,
-                0, nullptr, nullptr, 0, 0, 0, DINode::FlagZero, nullptr, 0,
-                nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                nullptr));
-  EXPECT_EQ(dwarf::DW_TAG_structure_type, CT.getTag());
+  EXPECT_EQ(&CT, DICompositeType::buildODRType(
+                     Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr,
+                     0, nullptr, nullptr, 0, 0, 0, DINode::FlagZero, nullptr, 0,
+                     nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                     nullptr, nullptr));
+  EXPECT_FALSE(CT.isForwardDecl());
 
   // Further updates should be ignored.
-  EXPECT_EQ(&CT,
-            DICompositeType::buildODRType(
-                Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr, 0,
-                nullptr, nullptr, 0, 0, 0, DINode::FlagFwdDecl, nullptr, 0,
-                nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                nullptr));
-  EXPECT_EQ(dwarf::DW_TAG_structure_type, CT.getTag());
-  EXPECT_EQ(&CT,
-            DICompositeType::buildODRType(
-                Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr, 0,
-                nullptr, nullptr, 0, 0, 0, DINode::FlagZero, nullptr, 0,
-                nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
-                nullptr));
-  EXPECT_EQ(dwarf::DW_TAG_structure_type, CT.getTag());
+  EXPECT_EQ(&CT, DICompositeType::buildODRType(
+                     Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr,
+                     0, nullptr, nullptr, 0, 0, 0, DINode::FlagFwdDecl, nullptr,
+                     0, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                     nullptr, nullptr));
+  EXPECT_FALSE(CT.isForwardDecl());
+  EXPECT_EQ(&CT, DICompositeType::buildODRType(
+                     Context, UUID, dwarf::DW_TAG_class_type, nullptr, nullptr,
+                     111u, nullptr, nullptr, 0, 0, 0, DINode::FlagZero, nullptr,
+                     0, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                     nullptr, nullptr));
+  EXPECT_NE(111u, CT.getLine());
 }
 
 TEST(DebugTypeODRUniquingTest, buildODRTypeFields) {
@@ -136,7 +136,6 @@
   DO_FOR_FIELD(VTableHolder)                                                   \
   DO_FOR_FIELD(TemplateParams)
 #define FOR_EACH_INLINEFIELD()                                                 \
-  DO_FOR_FIELD(Tag)                                                            \
   DO_FOR_FIELD(Line)                                                           \
   DO_FOR_FIELD(SizeInBits)                                                     \
   DO_FOR_FIELD(AlignInBits)                                                    \
@@ -155,10 +154,10 @@
   // Replace all the fields with new values that are distinct from each other.
   EXPECT_EQ(&CT,
             DICompositeType::buildODRType(
-                Context, UUID, Tag, Name, File, Line, Scope, BaseType,
-                SizeInBits, AlignInBits, OffsetInBits, DINode::FlagArtificial,
-                Elements, RuntimeLang, VTableHolder, TemplateParams, nullptr,
-                nullptr, nullptr, nullptr, nullptr, nullptr));
+                Context, UUID, 0, Name, File, Line, Scope, BaseType, SizeInBits,
+                AlignInBits, OffsetInBits, DINode::FlagArtificial, Elements,
+                RuntimeLang, VTableHolder, TemplateParams, nullptr, nullptr,
+                nullptr, nullptr, nullptr, nullptr));
 
   // Confirm that all the right fields got updated.
 #define DO_FOR_FIELD(X) EXPECT_EQ(X, CT.getRaw##X());