diff --git a/source/opt/merge_return_pass.cpp b/source/opt/merge_return_pass.cpp
index 6e7284b..b938b2f 100644
--- a/source/opt/merge_return_pass.cpp
+++ b/source/opt/merge_return_pass.cpp
@@ -81,6 +81,7 @@
     return false;
   }
 
+  RecordImmediateDominators(function);
   AddDummyLoopAroundFunction();
 
   std::list<BasicBlock*> order;
@@ -236,10 +237,6 @@
     inst->AddOperand({SPV_OPERAND_TYPE_ID, {new_source->id()}});
     context()->UpdateDefUse(inst);
   });
-
-  // Store the immediate dominator for this block in case new phi nodes will be
-  // needed later.
-  RecordImmediateDominator(target);
 }
 
 void MergeReturnPass::CreatePhiNodesForInst(BasicBlock* merge_block,
@@ -683,7 +680,7 @@
     return;
   }
 
-  BasicBlock* current_bb = new_merge_nodes_[bb];
+  BasicBlock* current_bb = context()->get_instr_block(original_dominator_[bb]);
   while (current_bb != nullptr && current_bb != dominator) {
     for (Instruction& inst : *current_bb) {
       CreatePhiNodesForInst(bb, inst);
@@ -692,11 +689,16 @@
   }
 }
 
-void MergeReturnPass::RecordImmediateDominator(BasicBlock* block) {
-  DominatorAnalysis* dom_tree =
-      context()->GetDominatorAnalysis(block->GetParent());
-  auto idom = dom_tree->ImmediateDominator(block);
-  new_merge_nodes_[block] = idom;
+void MergeReturnPass::RecordImmediateDominators(Function* function) {
+  DominatorAnalysis* dom_tree = context()->GetDominatorAnalysis(function);
+  for (BasicBlock& bb : *function) {
+    BasicBlock* dominator_bb = dom_tree->ImmediateDominator(&bb);
+    if (dominator_bb && dominator_bb != cfg()->pseudo_entry_block()) {
+      original_dominator_[&bb] = dominator_bb->terminator();
+    } else {
+      original_dominator_[&bb] = nullptr;
+    }
+  }
 }
 
 void MergeReturnPass::InsertAfterElement(BasicBlock* element,
diff --git a/source/opt/merge_return_pass.h b/source/opt/merge_return_pass.h
index d9eae39..f8edd27 100644
--- a/source/opt/merge_return_pass.h
+++ b/source/opt/merge_return_pass.h
@@ -246,24 +246,23 @@
   // instruction.
   void CreatePhiNodesForInst(BasicBlock* merge_block, Instruction& inst);
 
-  // Traverse the nodes in |new_merge_nodes_|, and adds the OpPhi instructions
-  // that are needed to make the code correct.  It is assumed that at this point
-  // there are no unreachable blocks in the control flow graph.
+  // Add new phi nodes for any id that no longer dominate all of it uses.  A phi
+  // node is added to a block |bb| for an id if the id is defined between the
+  // original immediate dominator of |bb| and its new immidiate dominator.  It
+  // is assumed that at this point there are no unreachable blocks in the
+  // control flow graph.
   void AddNewPhiNodes();
 
   // Creates any new phi nodes that are needed in |bb|.  |AddNewPhiNodes| must
   // have already been called on the original dominators of |bb|.
   void AddNewPhiNodes(BasicBlock* bb);
 
-  // Saves |block| to a list of basic block that will require OpPhi nodes to be
-  // added by calling |AddNewPhiNodes|.  It is assumed that |block| used to have
-  // a single predecessor, |single_original_pred|, but now has more.
-  void RecordImmediateDominator(BasicBlock* block);
+  // Records the terminator of immediate dominator for every basic block in
+  // |function|.
+  void RecordImmediateDominators(Function* function);
 
   // Modifies existing OpPhi instruction in |target| block to account for the
-  // new edge from |new_source|.  The value for that edge will be an Undef. If
-  // |target| only had a single predecessor, then it is marked as needing new
-  // phi nodes.  See |RecordImmediateDominator|.
+  // new edge from |new_source|.  The value for that edge will be an Undef.
   //
   // The CFG must not include the edge from |new_source| to |target| yet.
   void UpdatePhiNodes(BasicBlock* new_source, BasicBlock* target);
@@ -317,9 +316,10 @@
   // after processing the current function.
   BasicBlock* final_return_block_;
 
-  // This is a map from a node to its original immediate dominator.  This is
-  // used to determine which values will require a new phi node.
-  std::unordered_map<BasicBlock*, BasicBlock*> new_merge_nodes_;
+  // This is a map from a node to its original immediate dominator identified by
+  // the terminator if that block.  We use the terminator because the block we
+  // want may change if the block is split.
+  std::unordered_map<BasicBlock*, Instruction*> original_dominator_;
 
   // A map from a basic block, bb, to the set of basic blocks which represent
   // the new edges that reach |bb|.
diff --git a/test/opt/pass_merge_return_test.cpp b/test/opt/pass_merge_return_test.cpp
index f6b30de..baf7820 100644
--- a/test/opt/pass_merge_return_test.cpp
+++ b/test/opt/pass_merge_return_test.cpp
@@ -1779,6 +1779,57 @@
   SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
   SinglePassRunAndMatch<MergeReturnPass>(text, true);
 }
+TEST_F(MergeReturnPassTest, PhiInSecondMerge) {
+  //  Add and use a phi in the second merge block from the return.
+  const std::string text =
+      R"(
+; CHECK: OpLoopMerge
+; CHECK: OpLoopMerge [[merge_bb:%\w+]] [[continue_bb:%\w+]]
+; CHECK: [[continue_bb]] = OpLabel
+; CHECK-NEXT: [[val:%\w+]] = OpUndef %float
+; CHECK: [[merge_bb]] = OpLabel
+; CHECK-NEXT: [[phi:%\w+]] = OpPhi %float {{%\w+}} {{%\w+}} [[val]] [[continue_bb]]
+; CHECK-NOT: OpLabel
+; CHECK: OpBranchConditional {{%\w+}} {{%\w+}} [[old_merge:%\w+]]
+; CHECK: [[old_merge]] = OpLabel
+; CHECK-NEXT: OpConvertFToS %int [[phi]]
+               OpCapability Shader
+          %1 = OpExtInstImport "GLSL.std.450"
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint Fragment %2 "main"
+               OpExecutionMode %2 OriginUpperLeft
+               OpSource ESSL 310
+       %void = OpTypeVoid
+          %4 = OpTypeFunction %void
+        %int = OpTypeInt 32 1
+      %float = OpTypeFloat 32
+       %bool = OpTypeBool
+          %8 = OpUndef %bool
+          %2 = OpFunction %void None %4
+          %9 = OpLabel
+               OpBranch %10
+         %10 = OpLabel
+               OpLoopMerge %11 %12 None
+               OpBranch %13
+         %13 = OpLabel
+               OpLoopMerge %12 %14 None
+               OpBranchConditional %8 %15 %12
+         %15 = OpLabel
+               OpReturn
+         %14 = OpLabel
+               OpBranch %13
+         %12 = OpLabel
+         %16 = OpUndef %float
+               OpBranchConditional %8 %10 %11
+         %11 = OpLabel
+         %17 = OpConvertFToS %int %16
+               OpReturn
+               OpFunctionEnd
+)";
+
+  SetAssembleOptions(SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  SinglePassRunAndMatch<MergeReturnPass>(text, true);
+}
 
 }  // namespace
 }  // namespace opt