diff --git a/CHANGES b/CHANGES
index ffe7b0006..8347371dd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -16,6 +16,8 @@ v2016.7-dev 2017-01-06
      header.
    #548: Validator: Error when the reserved OpImageSparseSampleProj* opcodes
      are used.
+   #611: spvtools::Optimizer was failing to save the module to the output
+     binary vector when all passes succeded without changes.
 
 v2016.6 2016-12-13
  - Published the C++ interface for assembling, disassembling, validation, and
diff --git a/source/opt/optimizer.cpp b/source/opt/optimizer.cpp
index f6dc1cdf4..b1d71973d 100644
--- a/source/opt/optimizer.cpp
+++ b/source/opt/optimizer.cpp
@@ -75,7 +75,10 @@ bool Optimizer::Run(const uint32_t* original_binary,
   if (module == nullptr) return false;
 
   auto status = impl_->pass_manager.Run(module.get());
-  if (status == opt::Pass::Status::SuccessWithChange) {
+  if (status == opt::Pass::Status::SuccessWithChange ||
+      (status == opt::Pass::Status::SuccessWithoutChange &&
+       (optimized_binary->data() != original_binary ||
+        optimized_binary->size() != original_binary_size))) {
     optimized_binary->clear();
     module->ToBinary(optimized_binary, /* skip_nop = */ true);
   }
diff --git a/test/opt/CMakeLists.txt b/test/opt/CMakeLists.txt
index 2f1f482ac..d807d47c5 100644
--- a/test/opt/CMakeLists.txt
+++ b/test/opt/CMakeLists.txt
@@ -28,6 +28,11 @@ add_spvtools_unittest(TARGET pass_manager
   LIBS SPIRV-Tools-opt
 )
 
+add_spvtools_unittest(TARGET optimizer
+  SRCS optimizer_test.cpp
+  LIBS SPIRV-Tools-opt
+)
+
 add_spvtools_unittest(TARGET pass_strip_debug_info
   SRCS strip_debug_info_test.cpp pass_utils.cpp
   LIBS SPIRV-Tools-opt
diff --git a/test/opt/optimizer_test.cpp b/test/opt/optimizer_test.cpp
new file mode 100644
index 000000000..ef0e99213
--- /dev/null
+++ b/test/opt/optimizer_test.cpp
@@ -0,0 +1,109 @@
+// Copyright (c) 2017 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <gmock/gmock.h>
+
+#include "spirv-tools/libspirv.hpp"
+#include "spirv-tools/optimizer.hpp"
+
+#include "pass_fixture.h"
+
+namespace {
+
+using spvtools::CreateNullPass;
+using spvtools::CreateStripDebugInfoPass;
+using spvtools::Optimizer;
+using spvtools::SpirvTools;
+using ::testing::Eq;
+
+TEST(Optimizer, CanRunNullPassWithDistinctInputOutputVectors) {
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_0);
+  std::vector<uint32_t> binary_in;
+  tools.Assemble("OpName %foo \"foo\"\n%foo = OpTypeVoid", &binary_in);
+
+  Optimizer opt(SPV_ENV_UNIVERSAL_1_0);
+  opt.RegisterPass(CreateNullPass());
+  std::vector<uint32_t> binary_out;
+  opt.Run(binary_in.data(), binary_in.size(), &binary_out);
+
+  std::string disassembly;
+  tools.Disassemble(binary_out.data(), binary_out.size(), &disassembly);
+  EXPECT_THAT(disassembly, Eq("OpName %foo \"foo\"\n%foo = OpTypeVoid\n"));
+}
+
+TEST(Optimizer, CanRunTransformingPassWithDistinctInputOutputVectors) {
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_0);
+  std::vector<uint32_t> binary_in;
+  tools.Assemble("OpName %foo \"foo\"\n%foo = OpTypeVoid", &binary_in);
+
+  Optimizer opt(SPV_ENV_UNIVERSAL_1_0);
+  opt.RegisterPass(CreateStripDebugInfoPass());
+  std::vector<uint32_t> binary_out;
+  opt.Run(binary_in.data(), binary_in.size(), &binary_out);
+
+  std::string disassembly;
+  tools.Disassemble(binary_out.data(), binary_out.size(), &disassembly);
+  EXPECT_THAT(disassembly, Eq("%void = OpTypeVoid\n"));
+}
+
+TEST(Optimizer, CanRunNullPassWithAliasedVectors) {
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_0);
+  std::vector<uint32_t> binary;
+  tools.Assemble("OpName %foo \"foo\"\n%foo = OpTypeVoid", &binary);
+
+  Optimizer opt(SPV_ENV_UNIVERSAL_1_0);
+  opt.RegisterPass(CreateNullPass());
+  opt.Run(binary.data(), binary.size(), &binary);  // This is the key.
+
+  std::string disassembly;
+  tools.Disassemble(binary.data(), binary.size(), &disassembly);
+  EXPECT_THAT(disassembly, Eq("OpName %foo \"foo\"\n%foo = OpTypeVoid\n"));
+}
+
+TEST(Optimizer, CanRunNullPassWithAliasedVectorDataButDifferentSize) {
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_0);
+  std::vector<uint32_t> binary;
+  tools.Assemble("OpName %foo \"foo\"\n%foo = OpTypeVoid", &binary);
+
+  Optimizer opt(SPV_ENV_UNIVERSAL_1_0);
+  opt.RegisterPass(CreateNullPass());
+  auto orig_size = binary.size();
+  // Now change the size.  Add a word that will be ignored
+  // by the optimizer.
+  binary.push_back(42);
+  EXPECT_THAT(orig_size + 1, Eq(binary.size()));
+  opt.Run(binary.data(), orig_size, &binary);  // This is the key.
+  // The binary vector should have been rewritten.
+  EXPECT_THAT(binary.size(), Eq(orig_size));
+
+  std::string disassembly;
+  tools.Disassemble(binary.data(), binary.size(), &disassembly);
+  EXPECT_THAT(disassembly, Eq("OpName %foo \"foo\"\n%foo = OpTypeVoid\n"));
+}
+
+TEST(Optimizer, CanRunTransformingPassWithAliasedVectors) {
+  SpirvTools tools(SPV_ENV_UNIVERSAL_1_0);
+  std::vector<uint32_t> binary;
+  tools.Assemble("OpName %foo \"foo\"\n%foo = OpTypeVoid", &binary);
+
+  Optimizer opt(SPV_ENV_UNIVERSAL_1_0);
+  opt.RegisterPass(CreateStripDebugInfoPass());
+  opt.Run(binary.data(), binary.size(), &binary);  // This is the key
+
+  std::string disassembly;
+  tools.Disassemble(binary.data(), binary.size(), &disassembly);
+  EXPECT_THAT(disassembly, Eq("%void = OpTypeVoid\n"));
+}
+
+}  // namespace