diff --git a/.travis.yml b/.travis.yml
index c7f879a70..4dae911dd 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,8 +9,8 @@ addons:
       - pkg-config
 
 before_install:
-  - wget https://github.com/bazelbuild/bazel/releases/download/0.9.0/bazel_0.9.0-linux-x86_64.deb
-  - sudo dpkg -i bazel_0.9.0-linux-x86_64.deb
+  - wget https://github.com/bazelbuild/bazel/releases/download/0.17.2/bazel_0.17.2-linux-x86_64.deb
+  - sudo dpkg -i bazel_0.17.2-linux-x86_64.deb
 
 script:
   - bazel test ...
diff --git a/WORKSPACE b/WORKSPACE
index 610b4b954..cdf03eb12 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -6,8 +6,8 @@ http_archive(
 
 http_archive(
     name = "com_google_protobuf",
-    strip_prefix = "protobuf-3.5.0",
-    urls = ["https://github.com/google/protobuf/archive/v3.5.0.zip"],
+    strip_prefix = "protobuf-3.5.1",
+    urls = ["https://github.com/google/protobuf/archive/v3.5.1.zip"],
 )
 
 http_archive(
diff --git a/common/BUILD.bazel b/common/BUILD.bazel
index afebdb142..faecb9bc5 100644
--- a/common/BUILD.bazel
+++ b/common/BUILD.bazel
@@ -184,9 +184,6 @@ cc_library(
 cc_test(
     name = "converters_test",
     srcs = ["converters_test.cc"],
-    data = [
-        "@com_google_cel_spec//testdata",
-    ],
     deps = [
         ":converters",
         ":value",
@@ -194,13 +191,3 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
-
-cc_library(
-    name = "cel_operators",
-    srcs = [
-        "cel_operators.cc",
-    ],
-    hdrs = [
-        "cel_operators.h",
-    ],
-)
diff --git a/common/cel_operators.cc b/common/cel_operators.cc
deleted file mode 100644
index f1d91f081..000000000
--- a/common/cel_operators.cc
+++ /dev/null
@@ -1,34 +0,0 @@
-#include "common/cel_operators.h"
-
-namespace google {
-namespace api {
-namespace expr {
-
-constexpr char Operators::CONDITIONAL_NAME[];
-constexpr char Operators::LOGICAL_AND_NAME[];
-constexpr char Operators::LOGICAL_OR_NAME[];
-constexpr char Operators::LOGICAL_NOT_NAME[];
-constexpr char Operators::IN_NAME[];
-constexpr char Operators::EQUALS_NAME[];
-constexpr char Operators::NOT_EQUALS_NAME[];
-constexpr char Operators::LESS_NAME[];
-constexpr char Operators::LESS_EQUALS_NAME[];
-constexpr char Operators::GREATER_NAME[];
-constexpr char Operators::GREATER_EQUALS_NAME[];
-constexpr char Operators::ADD_NAME[];
-constexpr char Operators::SUBTRACT_NAME[];
-constexpr char Operators::MULTIPLY_NAME[];
-constexpr char Operators::DIVIDE_NAME[];
-constexpr char Operators::MODULO_NAME[];
-constexpr char Operators::NEGATE_NAME[];
-constexpr char Operators::INDEX_NAME[];
-constexpr char Operators::HAS_NAME[];
-constexpr char Operators::ALL_NAME[];
-constexpr char Operators::EXISTS_NAME[];
-constexpr char Operators::EXISTS_ONE_NAME[];
-constexpr char Operators::MAP_NAME[];
-constexpr char Operators::FILTER_NAME[];
-
-}  // namespace expr
-}  // namespace api
-}  // namespace google
diff --git a/common/cel_operators.h b/common/cel_operators.h
deleted file mode 100644
index ea6628a24..000000000
--- a/common/cel_operators.h
+++ /dev/null
@@ -1,40 +0,0 @@
-#ifndef THIRD_PARTY_CEL_CPP_COMMON_CEL_OPERATORS_H_
-#define THIRD_PARTY_CEL_CPP_COMMON_CEL_OPERATORS_H_
-
-namespace google {
-namespace api {
-namespace expr {
-
-class Operators {
- public:
-  static constexpr char CONDITIONAL_NAME[] = "_?_:_";
-  static constexpr char LOGICAL_AND_NAME[] = "_&&_";
-  static constexpr char LOGICAL_OR_NAME[] = "_||_";
-  static constexpr char LOGICAL_NOT_NAME[] = "!_";
-  static constexpr char IN_NAME[] = "_in_";
-  static constexpr char EQUALS_NAME[] = "_==_";
-  static constexpr char NOT_EQUALS_NAME[] = "_!=_";
-  static constexpr char LESS_NAME[] = "_<_";
-  static constexpr char LESS_EQUALS_NAME[] = "_<=_";
-  static constexpr char GREATER_NAME[] = "_>_";
-  static constexpr char GREATER_EQUALS_NAME[] = "_>=_";
-  static constexpr char ADD_NAME[] = "_+_";
-  static constexpr char SUBTRACT_NAME[] = "_-_";
-  static constexpr char MULTIPLY_NAME[] = "_*_";
-  static constexpr char DIVIDE_NAME[] = "_/_";
-  static constexpr char MODULO_NAME[] = "_%_";
-  static constexpr char NEGATE_NAME[] = "-_";
-  static constexpr char INDEX_NAME[] = "_[_]";
-  static constexpr char HAS_NAME[] = "has";
-  static constexpr char ALL_NAME[] = "all";
-  static constexpr char EXISTS_NAME[] = "exists";
-  static constexpr char EXISTS_ONE_NAME[] = "exists_one";
-  static constexpr char MAP_NAME[] = "map";
-  static constexpr char FILTER_NAME[] = "filter";
-};
-
-}  // namespace expr
-}  // namespace api
-}  // namespace google
-
-#endif  // THIRD_PARTY_CEL_CPP_COMMON_CEL_OPERATORS_H_
diff --git a/common/enum.h b/common/enum.h
index 0613e63dd..714f0597d 100644
--- a/common/enum.h
+++ b/common/enum.h
@@ -33,8 +33,8 @@ class UnnamedEnumValue final : public internal::RefCountable {
  public:
   ~UnnamedEnumValue() = default;
 
-  inline constexpr int32_t value() const { return value_; }
-  inline constexpr EnumType type() const { return type_; }
+  inline int32_t value() const { return value_; }
+  inline EnumType type() const { return type_; }
 
   std::string ToString() const;
 
diff --git a/common/type.cc b/common/type.cc
index fc9d7f845..d1300ebfe 100644
--- a/common/type.cc
+++ b/common/type.cc
@@ -10,7 +10,7 @@ namespace expr {
 namespace {
 
 constexpr const std::size_t kBasicTypeNamesSize = 10;
-const auto* kBasicTypeNames = new std::array<std::string, kBasicTypeNamesSize>{
+const auto* kBasicTypeNames = new std::array<std::string, kBasicTypeNamesSize>({
     "null_type",  // kNull
     "bool",       // kBool
     "int",        // kInt
@@ -21,7 +21,7 @@ const auto* kBasicTypeNames = new std::array<std::string, kBasicTypeNamesSize>{
     "type",       // kType
     "map",        // kMap
     "list",       // kList
-};
+});
 
 static_assert(kBasicTypeNamesSize ==
                   static_cast<int>(BasicTypeValue::DO_NOT_USE),
diff --git a/common/type.h b/common/type.h
index b9a9db3fa..57dcf9c95 100644
--- a/common/type.h
+++ b/common/type.h
@@ -137,10 +137,10 @@ class Type final {
   inline EnumType enum_type() const { return absl::get<EnumType>(data_); }
   inline ObjectType object_type() const { return absl::get<ObjectType>(data_); }
 
-  constexpr inline bool operator==(const Type& rhs) const {
+  inline bool operator==(const Type& rhs) const {
     return data_ == rhs.data_;
   }
-  constexpr inline bool operator!=(const Type& rhs) const {
+  inline bool operator!=(const Type& rhs) const {
     return data_ != rhs.data_;
   }
 
diff --git a/internal/hash_util.h b/internal/hash_util.h
index 8c025f13e..7caeadfbe 100644
--- a/internal/hash_util.h
+++ b/internal/hash_util.h
@@ -95,7 +95,7 @@ std::size_t HashImpl(const T& value, specialize_for<typename T::Hasher>) {
 
 // Specialization for enums.
 template <typename T>
-specialize_ift<std::is_enum<T>, std::size_t> HashImpl(T&& v) {
+std::size_t HashImpl(T&& v, specialize_ift<std::is_enum<T>>) {
   return Hash(static_cast<typename std::underlying_type<T>::type>(v));
 }