diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
index 772aa4079a6d8..a98cf5c56143e 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
@@ -656,7 +656,7 @@ class MLocTracker {
 
   // If we discover a new machine location, assign it an mphi with this
   // block number.
-  unsigned CurBB;
+  unsigned CurBB = 0;  // FIXME: https://reviews.llvm.org/D150420
 
   /// Cached local copy of the number of registers the target has.
   unsigned NumRegs;