diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 6060ef2449..43631977bb 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -815,11 +815,7 @@ void LChunkBuilder::DoBasicBlock(HBasicBlock* block, HBasicBlock* next_block) {
     HEnvironment* last_environment = pred->last_environment();
     for (int i = 0; i < block->phis()->length(); ++i) {
       HPhi* phi = block->phis()->at(i);
-      // TODO(mstarzinger): The length check below should actually not
-      // be necessary, but some array stubs already rely on it. This
-      // should be investigated and fixed.
-      if (phi->HasMergedIndex() &&
-          phi->merged_index() < last_environment->length()) {
+      if (phi->HasMergedIndex()) {
         last_environment->SetValueAt(phi->merged_index(), phi);
       }
     }
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index e5af9f8002..f90dc0b2ee 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -5701,6 +5701,7 @@ HValue* HOptimizedGraphBuilder::HandlePolymorphicElementAccess(
     if (!is_store) {
       Push(access);
     }
+    NoObservableSideEffectsScope scope(this);
     current_block()->GotoNoSimulate(join);
     set_current_block(other_map);
   }
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 323cd7211d..65637b4fbf 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -870,11 +870,7 @@ void LChunkBuilder::DoBasicBlock(HBasicBlock* block, HBasicBlock* next_block) {
     HEnvironment* last_environment = pred->last_environment();
     for (int i = 0; i < block->phis()->length(); ++i) {
       HPhi* phi = block->phis()->at(i);
-      // TODO(mstarzinger): The length check below should actually not
-      // be necessary, but some array stubs already rely on it. This
-      // should be investigated and fixed.
-      if (phi->HasMergedIndex() &&
-          phi->merged_index() < last_environment->length()) {
+      if (phi->HasMergedIndex()) {
         last_environment->SetValueAt(phi->merged_index(), phi);
       }
     }
diff --git a/src/mips/lithium-mips.cc b/src/mips/lithium-mips.cc
index 09ec478d5f..fa415e5ef2 100644
--- a/src/mips/lithium-mips.cc
+++ b/src/mips/lithium-mips.cc
@@ -820,11 +820,7 @@ void LChunkBuilder::DoBasicBlock(HBasicBlock* block, HBasicBlock* next_block) {
     HEnvironment* last_environment = pred->last_environment();
     for (int i = 0; i < block->phis()->length(); ++i) {
       HPhi* phi = block->phis()->at(i);
-      // TODO(mstarzinger): The length check below should actually not
-      // be necessary, but some array stubs already rely on it. This
-      // should be investigated and fixed.
-      if (phi->HasMergedIndex() &&
-          phi->merged_index() < last_environment->length()) {
+      if (phi->HasMergedIndex()) {
         last_environment->SetValueAt(phi->merged_index(), phi);
       }
     }
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index ac372b69fb..1b1de3484e 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -814,11 +814,7 @@ void LChunkBuilder::DoBasicBlock(HBasicBlock* block, HBasicBlock* next_block) {
     HEnvironment* last_environment = pred->last_environment();
     for (int i = 0; i < block->phis()->length(); ++i) {
       HPhi* phi = block->phis()->at(i);
-      // TODO(mstarzinger): The length check below should actually not
-      // be necessary, but some array stubs already rely on it. This
-      // should be investigated and fixed.
-      if (phi->HasMergedIndex() &&
-          phi->merged_index() < last_environment->length()) {
+      if (phi->HasMergedIndex()) {
         last_environment->SetValueAt(phi->merged_index(), phi);
       }
     }