diff --git a/llvm/lib/Transforms/Scalar/JumpThreading.cpp b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
index f2b9d784ead8a..7a8128c5b6c09 100644
--- a/llvm/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/llvm/lib/Transforms/Scalar/JumpThreading.cpp
@@ -761,7 +761,10 @@ bool JumpThreadingPass::computeValueKnownInPredecessorsImpl(
     PHINode *PN = dyn_cast<PHINode>(CmpLHS);
     if (!PN)
       PN = dyn_cast<PHINode>(CmpRHS);
-    if (PN && PN->getParent() == BB) {
+    // Do not perform phi translation across a loop header phi, because this
+    // may result in comparison of values from two different loop iterations.
+    // FIXME: This check is broken if LoopHeaders is not populated.
+    if (PN && PN->getParent() == BB && !LoopHeaders.contains(BB)) {
       const DataLayout &DL = PN->getModule()->getDataLayout();
       // We can do this simplification if any comparisons fold to true or false.
       // See if any do.
diff --git a/llvm/test/Transforms/JumpThreading/pr70651.ll b/llvm/test/Transforms/JumpThreading/pr70651.ll
index a156be541874a..2c6059bfdb3d5 100644
--- a/llvm/test/Transforms/JumpThreading/pr70651.ll
+++ b/llvm/test/Transforms/JumpThreading/pr70651.ll
@@ -1,7 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 3
 ; RUN: opt -S -passes=jump-threading < %s | FileCheck %s
+; RUN: opt -S -passes=jump-threading -jump-threading-across-loop-headers < %s | FileCheck %s --check-prefix=THREAD-LOOP
 
-; FIXME: This is a miscompile.
+; FIXME: This is a miscompile if -jump-threading-across-loop-headers is enabled.
 define i64 @test(i64 %v) {
 ; CHECK-LABEL: define i64 @test(
 ; CHECK-SAME: i64 [[V:%.*]]) {
@@ -12,10 +13,24 @@ define i64 @test(i64 %v) {
 ; CHECK-NEXT:    [[SUM:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[FOR_BODY]] ]
 ; CHECK-NEXT:    [[SUM_NEXT]] = add i64 [[SUM]], [[V]]
 ; CHECK-NEXT:    [[OVERFLOW:%.*]] = icmp ult i64 [[SUM_NEXT]], [[SUM]]
-; CHECK-NEXT:    br i1 [[V_NONNEG]], label [[FOR_BODY]], label [[EXIT:%.*]]
+; CHECK-NEXT:    [[CMP:%.*]] = xor i1 [[V_NONNEG]], [[OVERFLOW]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[EXIT:%.*]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i64 [[SUM]]
 ;
+; THREAD-LOOP-LABEL: define i64 @test(
+; THREAD-LOOP-SAME: i64 [[V:%.*]]) {
+; THREAD-LOOP-NEXT:  entry:
+; THREAD-LOOP-NEXT:    [[V_NONNEG:%.*]] = icmp sgt i64 [[V]], -1
+; THREAD-LOOP-NEXT:    br label [[FOR_BODY:%.*]]
+; THREAD-LOOP:       for.body:
+; THREAD-LOOP-NEXT:    [[SUM:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[SUM_NEXT:%.*]], [[FOR_BODY]] ]
+; THREAD-LOOP-NEXT:    [[SUM_NEXT]] = add i64 [[SUM]], [[V]]
+; THREAD-LOOP-NEXT:    [[OVERFLOW:%.*]] = icmp ult i64 [[SUM_NEXT]], [[SUM]]
+; THREAD-LOOP-NEXT:    br i1 [[V_NONNEG]], label [[FOR_BODY]], label [[EXIT:%.*]]
+; THREAD-LOOP:       exit:
+; THREAD-LOOP-NEXT:    ret i64 [[SUM]]
+;
 entry:
   %v.nonneg = icmp sgt i64 %v, -1
   br label %for.body