diff --git a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
--- a/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopFlatten.cpp
@@ -722,12 +722,14 @@
 
   // Fix up PHI nodes that take values from the inner loop back-edge, which
   // we are about to remove.
-  FI.InnerInductionPHI->removeIncomingValue(FI.InnerLoop->getLoopLatch());
+  SE->forgetBlockAndLoopDispositions(
+      FI.InnerInductionPHI->removeIncomingValue(FI.InnerLoop->getLoopLatch()));
 
   // The old Phi will be optimised away later, but for now we can't leave
   // leave it in an invalid state, so are updating them too.
   for (PHINode *PHI : FI.InnerPHIsToTransform)
-    PHI->removeIncomingValue(FI.InnerLoop->getLoopLatch());
+    SE->forgetBlockAndLoopDispositions(
+        PHI->removeIncomingValue(FI.InnerLoop->getLoopLatch()));
 
   // Modify the trip count of the outer loop to be the product of the two
   // trip counts.
diff --git a/llvm/test/Transforms/LoopFlatten/pr58865.ll b/llvm/test/Transforms/LoopFlatten/pr58865.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Transforms/LoopFlatten/pr58865.ll
@@ -0,0 +1,28 @@
+; RUN: opt -loop-flatten -verify-scev < %s
+
+define void @sum_2d(ptr %p) {
+entry:
+  br label %outer
+
+outer:                                         ; preds = %outer.latch, %entry
+  %sum.04 = phi i16 [ 0, %entry ], [ %0, %outer.latch ]
+  %outer.iv = phi i16 [ 0, %entry ], [ %outer.iv.next, %outer.latch ]
+  br label %inner
+
+inner:                                        ; preds = %inner, %outer
+  %sum.12 = phi i16 [ %sum.04, %outer ], [ %0, %inner ]
+  %inner.iv = phi i16 [ 0, %outer ], [ %inner.iv.next, %inner ]
+  %0 = load i16, ptr %p, align 1
+  %inner.iv.next = add nsw i16 %inner.iv, 1
+  %cmp2 = icmp slt i16 %inner.iv, 0
+  br i1 %cmp2, label %inner, label %outer.latch
+
+outer.latch:                                         ; preds = %inner
+  %outer.iv.next = add nsw i16 %outer.iv, 1
+  %cmp = icmp slt i16 %outer.iv.next, 0
+  br i1 %cmp, label %outer, label %exit
+
+exit:                                         ; preds = %outer.latch
+  ret void
+
+}