diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index f02ff2252f7d..a4faf22b8294 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6675,11 +6675,6 @@ bool SimplifyCFGOpt::simplifyOnceImpl(BasicBlock *BB) {
 }
 
 bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
-  assert((!RequireAndPreserveDomTree ||
-          (DTU &&
-           DTU->getDomTree().verify(DominatorTree::VerificationLevel::Full))) &&
-         "Original domtree is invalid?");
-
   bool Changed = simplifyOnceImpl(BB);
 
   assert((!RequireAndPreserveDomTree ||
@@ -6691,6 +6686,11 @@ bool SimplifyCFGOpt::simplifyOnce(BasicBlock *BB) {
 }
 
 bool SimplifyCFGOpt::run(BasicBlock *BB) {
+  assert((!RequireAndPreserveDomTree ||
+          (DTU &&
+           DTU->getDomTree().verify(DominatorTree::VerificationLevel::Full))) &&
+         "Original domtree is invalid?");
+
   bool Changed = false;
 
   // Repeated simplify BB as long as resimplification is requested.