diff --git a/llvm/include/llvm/CodeGen/MIRYamlMapping.h b/llvm/include/llvm/CodeGen/MIRYamlMapping.h
index 777819f3eae3..43c4a5dd6e37 100644
--- a/llvm/include/llvm/CodeGen/MIRYamlMapping.h
+++ b/llvm/include/llvm/CodeGen/MIRYamlMapping.h
@@ -300,7 +300,7 @@ template <> struct MappingTraits<MachineConstantPoolValue> {
 
 struct MachineJumpTable {
   struct Entry {
-    unsigned ID;
+    UnsignedValue ID;
     std::vector<FlowStringValue> Blocks;
   };
 
diff --git a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
index cc277eea9f4b..0679ec02c988 100644
--- a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
@@ -582,8 +582,11 @@ bool MIRParserImpl::initializeJumpTableInfo(
       Blocks.push_back(MBB);
     }
     unsigned Index = JTI->createJumpTableIndex(Blocks);
-    // TODO: Report an error when the same jump table slot ID is redefined.
-    PFS.JumpTableSlots.insert(std::make_pair(Entry.ID, Index));
+    if (!PFS.JumpTableSlots.insert(std::make_pair(Entry.ID.Value, Index))
+             .second)
+      return error(Entry.ID.SourceRange.Start,
+                   Twine("redefinition of jump table entry '%jump-table.") +
+                       Twine(Entry.ID.Value) + "'");
   }
   return false;
 }
diff --git a/llvm/test/CodeGen/MIR/X86/jump-table-redefinition-error.mir b/llvm/test/CodeGen/MIR/X86/jump-table-redefinition-error.mir
new file mode 100644
index 000000000000..c9d195adbd93
--- /dev/null
+++ b/llvm/test/CodeGen/MIR/X86/jump-table-redefinition-error.mir
@@ -0,0 +1,82 @@
+# RUN: not llc -march=x86-64 -start-after branch-folder -stop-after branch-folder -o /dev/null %s 2>&1 | FileCheck %s
+
+--- |
+
+  define i32 @test_jumptable(i32 %in) {
+  entry:
+    switch i32 %in, label %def [
+      i32 0, label %lbl1
+      i32 1, label %lbl2
+      i32 2, label %lbl3
+      i32 3, label %lbl4
+    ]
+
+  def:
+    ret i32 0
+
+  lbl1:
+    ret i32 1
+
+  lbl2:
+    ret i32 2
+
+  lbl3:
+    ret i32 4
+
+  lbl4:
+    ret i32 8
+  }
+
+...
+---
+name:            test_jumptable
+jumpTable:
+  kind:          label-difference32
+  entries:
+    - id:        0
+      blocks:    [ '%bb.3.lbl1', '%bb.4.lbl2', '%bb.5.lbl3', '%bb.6.lbl4' ]
+# CHECK: [[@LINE+1]]:18: redefinition of jump table entry '%jump-table.0'
+    - id:        0
+      blocks:    [ '%bb.3.lbl1', '%bb.4.lbl2', '%bb.5.lbl3', '%bb.6.lbl4' ]
+body:
+  - id:          0
+    name:        entry
+    successors:  [ '%bb.2.def', '%bb.1.entry' ]
+    instructions:
+      - '%eax = MOV32rr %edi, implicit-def %rax'
+      - 'CMP32ri8 %edi, 3, implicit-def %eflags'
+      - 'JA_1 %bb.2.def, implicit %eflags'
+  - id:          1
+    name:        entry
+    successors:  [ '%bb.3.lbl1', '%bb.4.lbl2', '%bb.5.lbl3', '%bb.6.lbl4' ]
+    instructions:
+      - '%rcx = LEA64r %rip, 1, _, %jump-table.0, _'
+      - '%rax = MOVSX64rm32 %rcx, 4, %rax, 0, _'
+      - '%rax = ADD64rr %rax, %rcx, implicit-def %eflags'
+      - 'JMP64r %rax'
+  - id:          2
+    name:        def
+    instructions:
+      - '%eax = MOV32r0 implicit-def %eflags'
+      - 'RETQ %eax'
+  - id:          3
+    name:        lbl1
+    instructions:
+      - '%eax = MOV32ri 1'
+      - 'RETQ %eax'
+  - id:          4
+    name:        lbl2
+    instructions:
+      - '%eax = MOV32ri 2'
+      - 'RETQ %eax'
+  - id:          5
+    name:        lbl3
+    instructions:
+      - '%eax = MOV32ri 4'
+      - 'RETQ %eax'
+  - id:          6
+    name:        lbl4
+    instructions:
+      - '%eax = MOV32ri 8'
+      - 'RETQ %eax'
+...