diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -683,6 +683,11 @@
   if (isa<UndefValue>(Idx))
     return PoisonValue::get(Val->getType());
 
+  // Inserting null into all zeros is still all zeros.
+  // TODO: This is true for undef and poison splats too.
+  if (isa<ConstantAggregateZero>(Val) && Elt->isNullValue())
+    return Val;
+
   ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx);
   if (!CIdx) return nullptr;
 
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll b/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
--- a/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/InsertElement.ll
@@ -50,3 +50,19 @@
   %E = extractelement <2 x i64> <i64 -1, i64 -1>, i64 undef
   ret i64 %E
 }
+
+define <vscale x 2 x i32> @insertelement_scalable_null() {
+; CHECK-LABEL: @insertelement_scalable_null(
+; CHECK-NEXT:    ret <vscale x 2 x i32> zeroinitializer
+;
+  %vec = insertelement <vscale x 2 x i32> zeroinitializer, i32 0, i32 0
+  ret <vscale x 2 x i32> %vec
+}
+
+define <vscale x 2 x float> @insertelement_scalable_null_fp() {
+; CHECK-LABEL: @insertelement_scalable_null_fp(
+; CHECK-NEXT:    ret <vscale x 2 x float> zeroinitializer
+;
+  %vec = insertelement <vscale x 2 x float> zeroinitializer, float 0.0, i32 1
+  ret <vscale x 2 x float> %vec
+}
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll b/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
--- a/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/sve-widen-phi.ll
@@ -251,7 +251,7 @@
 ; CHECK:       vector.body:
 ; CHECK-NEXT:    [[POINTER_PHI:%.*]] = phi i32* [ [[A]], [[VECTOR_PH]] ], [ [[PTR_IND:%.*]], [[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[INDEX:%.*]] = phi i64 [ 0, [[VECTOR_PH]] ], [ [[INDEX_NEXT:%.*]], [[VECTOR_BODY]] ]
-; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <vscale x 2 x i32> [ insertelement (<vscale x 2 x i32> zeroinitializer, i32 0, i32 0), [[VECTOR_PH]] ], [ [[TMP9:%.*]], [[VECTOR_BODY]] ]
+; CHECK-NEXT:    [[VEC_PHI:%.*]] = phi <vscale x 2 x i32> [ zeroinitializer, [[VECTOR_PH]] ], [ [[TMP9:%.*]], [[VECTOR_BODY]] ]
 ; CHECK-NEXT:    [[TMP4:%.*]] = call i64 @llvm.vscale.i64()
 ; CHECK-NEXT:    [[TMP5:%.*]] = shl nuw nsw i64 [[TMP4]], 1
 ; CHECK-NEXT:    [[TMP6:%.*]] = call <vscale x 2 x i64> @llvm.experimental.stepvector.nxv2i64()