diff --git a/lib/CodeGen/LiveRangeCalc.cpp b/lib/CodeGen/LiveRangeCalc.cpp
index 281cf1fb5a8..9f6262bd9a9 100644
--- a/lib/CodeGen/LiveRangeCalc.cpp
+++ b/lib/CodeGen/LiveRangeCalc.cpp
@@ -361,14 +361,14 @@ bool LiveRangeCalc::findReachingDefs(LiveRange &LR, MachineBasicBlock &UseMBB,
     MachineBasicBlock *MBB = MF->getBlockNumbered(WorkList[i]);
 
 #ifndef NDEBUG
-    if (Undefs.size() > 0 && MBB->pred_empty()) {
+    if (MBB->pred_empty()) {
       MBB->getParent()->verify();
       errs() << "Use of " << PrintReg(PhysReg)
              << " does not have a corresponding definition on every path:\n";
       const MachineInstr *MI = Indexes->getInstructionFromIndex(Use);
       if (MI != nullptr)
         errs() << Use << " " << *MI;
-      llvm_unreachable("Use not jointly dominated by defs.");
+      report_fatal_error("Use not jointly dominated by defs.");
     }
 
     if (TargetRegisterInfo::isPhysicalRegister(PhysReg) &&
@@ -378,7 +378,7 @@ bool LiveRangeCalc::findReachingDefs(LiveRange &LR, MachineBasicBlock &UseMBB,
       errs() << "The register " << PrintReg(PhysReg, TRI)
              << " needs to be live in to BB#" << MBB->getNumber()
              << ", but is missing from the live-in list.\n";
-      llvm_unreachable("Invalid global physical register");
+      report_fatal_error("Invalid global physical register");
     }
 #endif
     FoundUndef |= MBB->pred_empty();
diff --git a/test/CodeGen/X86/invalid-liveness.mir b/test/CodeGen/X86/invalid-liveness.mir
new file mode 100644
index 00000000000..ca862472ba8
--- /dev/null
+++ b/test/CodeGen/X86/invalid-liveness.mir
@@ -0,0 +1,31 @@
+# RUN: not llc -march=x86 -run-pass liveintervals -o - %s 2>&1 | FileCheck %s
+# REQUIRES: asserts
+
+--- |
+  define void @func() { ret void }
+...
+---
+# Liveness calculation should detect that we do not have a definition for vreg0
+# on all paths; In this example a def for vreg0 is missing when jumping from
+# bb.0 to bb.3.
+#
+# CHECK: Use of %vreg0 does not have a corresponding definition on every path
+# CHECK: ERROR: Use not jointly dominated by defs.
+name: func
+registers:
+  - { id: 0, class: gr32 }
+body: |
+  bb.0:
+    successors: %bb.2, %bb.3
+    JG_1 %bb.2, implicit %eflags
+    JMP_1 %bb.3
+
+  bb.2:
+    successors: %bb.3
+    %0 = IMPLICIT_DEF
+    JMP_1 %bb.3
+
+  bb.3:
+    %eax = COPY %0
+    RETQ %eax
+...