Index: lib/Transforms/Utils/Local.cpp
===================================================================
--- lib/Transforms/Utils/Local.cpp
+++ lib/Transforms/Utils/Local.cpp
@@ -2265,8 +2265,16 @@
 
   if (DTU) {
     DTU->applyUpdates(Updates, /*ForceRemoveDuplicates*/ true);
-    for (auto *BB : ToDeleteBBs)
+    bool Deleted = false;
+    for (auto *BB : ToDeleteBBs) {
+      if (DTU->isBBPendingDeletion(BB))
+        --NumRemoved;
+      else
+        Deleted = true;
       DTU->deleteBB(BB);
+    }
+    if (!Deleted)
+      return false;
   }
   return true;
 }
Index: unittests/Transforms/Utils/Local.cpp
===================================================================
--- unittests/Transforms/Utils/Local.cpp
+++ unittests/Transforms/Utils/Local.cpp
@@ -838,4 +838,23 @@
   runWithDomTree(*M, "br_self_loop", runLazy);
   runWithDomTree(*M, "br_constant", runLazy);
   runWithDomTree(*M, "br_loop", runLazy);
+
+  M = parseIR(C,
+              R"(
+      define void @f() {
+      entry:
+        ret void
+      bb0:
+        ret void
+      }
+        )");
+
+  auto checkRUBlocksRetVal = [&](Function &F, DominatorTree *DT) {
+    DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Lazy);
+    EXPECT_TRUE(removeUnreachableBlocks(F, nullptr, &DTU));
+    EXPECT_FALSE(removeUnreachableBlocks(F, nullptr, &DTU));
+    EXPECT_TRUE(DTU.getDomTree().verify());
+  };
+
+  runWithDomTree(*M, "f", checkRUBlocksRetVal);
 }
\ No newline at end of file