diff --git a/common/certificate_checker.cc b/common/certificate_checker.cc
index b8d8c94..86df950 100644
--- a/common/certificate_checker.cc
+++ b/common/certificate_checker.cc
@@ -18,12 +18,10 @@
 
 #include <string>
 
-#include <base/lazy_instance.h>
 #include <base/logging.h>
 #include <base/strings/string_number_conversions.h>
 #include <base/strings/string_util.h>
 #include <base/strings/stringprintf.h>
-#include <base/threading/thread_local.h>
 #include <curl/curl.h>
 #include <openssl/evp.h>
 #include <openssl/ssl.h>
@@ -36,13 +34,6 @@
 
 namespace chromeos_update_engine {
 
-namespace {
-// A lazily created thread local storage for passing the current certificate
-// checker to the openssl callback.
-base::LazyInstance<base::ThreadLocalPointer<CertificateChecker>>::Leaky
-    lazy_tls_ptr;
-}  // namespace
-
 bool OpenSSLWrapper::GetCertificateDigest(X509_STORE_CTX* x509_ctx,
                                           int* out_depth,
                                           unsigned int* out_digest_length,
@@ -63,53 +54,92 @@
   return success;
 }
 
+// static
+CertificateChecker* CertificateChecker::cert_checker_singleton_ = nullptr;
+
 CertificateChecker::CertificateChecker(PrefsInterface* prefs,
-                                       OpenSSLWrapper* openssl_wrapper,
-                                       ServerToCheck server_to_check)
-    : prefs_(prefs),
-      openssl_wrapper_(openssl_wrapper),
-      server_to_check_(server_to_check) {
+                                       OpenSSLWrapper* openssl_wrapper)
+    : prefs_(prefs), openssl_wrapper_(openssl_wrapper) {
+}
+
+CertificateChecker::~CertificateChecker() {
+  if (cert_checker_singleton_ == this)
+    cert_checker_singleton_ = nullptr;
+}
+
+void CertificateChecker::Init() {
+  CHECK(cert_checker_singleton_ == nullptr);
+  cert_checker_singleton_ = this;
 }
 
 // static
 CURLcode CertificateChecker::ProcessSSLContext(CURL* curl_handle,
                                                SSL_CTX* ssl_ctx,
                                                void* ptr) {
-  CertificateChecker* cert_checker = reinterpret_cast<CertificateChecker*>(ptr);
+  ServerToCheck* server_to_check = reinterpret_cast<ServerToCheck*>(ptr);
+
+  if (!cert_checker_singleton_) {
+    DLOG(WARNING) << "No CertificateChecker singleton initialized.";
+    return CURLE_FAILED_INIT;
+  }
 
   // From here we set the SSL_CTX to another callback, from the openssl library,
   // which will be called after each server certificate is validated. However,
   // since openssl does not allow us to pass our own data pointer to the
-  // callback, the certificate check will have to be done statically. To pass
-  // the pointer to this instance, we use a thread-safe pointer in lazy_tls_ptr
-  // during the calls and clear them after it.
-  CHECK(cert_checker != nullptr);
-  lazy_tls_ptr.Pointer()->Set(cert_checker);
-  SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, VerifySSLCallback);
-  // Sanity check: We should not re-enter this method during certificate
-  // checking.
-  CHECK(lazy_tls_ptr.Pointer()->Get() == cert_checker);
-  lazy_tls_ptr.Pointer()->Set(nullptr);
+  // callback, the certificate check will have to be done statically. Since we
+  // need to know which update server we are using in order to check the
+  // certificate, we hardcode Chrome OS's two known update servers here, and
+  // define a different static callback for each. Since this code should only
+  // run in official builds, this should not be a problem. However, if an update
+  // server different from the ones listed here is used, the check will not
+  // take place.
+  int (*verify_callback)(int, X509_STORE_CTX*);
+  switch (*server_to_check) {
+    case ServerToCheck::kDownload:
+      verify_callback = &CertificateChecker::VerifySSLCallbackDownload;
+      break;
+    case ServerToCheck::kUpdate:
+      verify_callback = &CertificateChecker::VerifySSLCallbackUpdate;
+      break;
+    case ServerToCheck::kNone:
+      verify_callback = nullptr;
+      break;
+  }
 
+  SSL_CTX_set_verify(ssl_ctx, SSL_VERIFY_PEER, verify_callback);
   return CURLE_OK;
 }
 
 // static
+int CertificateChecker::VerifySSLCallbackDownload(int preverify_ok,
+                                                  X509_STORE_CTX* x509_ctx) {
+  return VerifySSLCallback(preverify_ok, x509_ctx, ServerToCheck::kDownload);
+}
+
+// static
+int CertificateChecker::VerifySSLCallbackUpdate(int preverify_ok,
+                                                X509_STORE_CTX* x509_ctx) {
+  return VerifySSLCallback(preverify_ok, x509_ctx, ServerToCheck::kUpdate);
+}
+
+// static
 int CertificateChecker::VerifySSLCallback(int preverify_ok,
-                                          X509_STORE_CTX* x509_ctx) {
-  CertificateChecker* cert_checker = lazy_tls_ptr.Pointer()->Get();
-  CHECK(cert_checker != nullptr);
-  return cert_checker->CheckCertificateChange(preverify_ok, x509_ctx) ? 1 : 0;
+                                          X509_STORE_CTX* x509_ctx,
+                                          ServerToCheck server_to_check) {
+  CHECK(cert_checker_singleton_ != nullptr);
+  return cert_checker_singleton_->CheckCertificateChange(
+      preverify_ok, x509_ctx, server_to_check) ? 1 : 0;
 }
 
 bool CertificateChecker::CheckCertificateChange(int preverify_ok,
-                                                X509_STORE_CTX* x509_ctx) {
+                                                X509_STORE_CTX* x509_ctx,
+                                                ServerToCheck server_to_check) {
   TEST_AND_RETURN_FALSE(prefs_ != nullptr);
 
   // If pre-verification failed, we are not interested in the current
   // certificate. We store a report to UMA and just propagate the fail result.
   if (!preverify_ok) {
-    NotifyCertificateChecked(CertificateCheckResult::kFailed);
+    NotifyCertificateChecked(server_to_check, CertificateCheckResult::kFailed);
     return false;
   }
 
@@ -123,7 +153,7 @@
                                               digest)) {
     LOG(WARNING) << "Failed to generate digest of X509 certificate "
                  << "from update server.";
-    NotifyCertificateChecked(CertificateCheckResult::kValid);
+    NotifyCertificateChecked(server_to_check, CertificateCheckResult::kValid);
     return true;
   }
 
@@ -133,7 +163,7 @@
 
   string storage_key =
       base::StringPrintf("%s-%d-%d", kPrefsUpdateServerCertificate,
-                         static_cast<int>(server_to_check_), depth);
+                         static_cast<int>(server_to_check), depth);
   string stored_digest;
   // If there's no stored certificate, we just store the current one and return.
   if (!prefs_->GetString(storage_key, &stored_digest)) {
@@ -141,7 +171,7 @@
       LOG(WARNING) << "Failed to store server certificate on storage key "
                    << storage_key;
     }
-    NotifyCertificateChecked(CertificateCheckResult::kValid);
+    NotifyCertificateChecked(server_to_check, CertificateCheckResult::kValid);
     return true;
   }
 
@@ -152,19 +182,23 @@
       LOG(WARNING) << "Failed to store server certificate on storage key "
                    << storage_key;
     }
-    NotifyCertificateChecked(CertificateCheckResult::kValidChanged);
+    LOG(INFO) << "Certificate changed from " << stored_digest << " to "
+              << digest_string << ".";
+    NotifyCertificateChecked(server_to_check,
+                             CertificateCheckResult::kValidChanged);
     return true;
   }
 
-  NotifyCertificateChecked(CertificateCheckResult::kValid);
+  NotifyCertificateChecked(server_to_check, CertificateCheckResult::kValid);
   // Since we don't perform actual SSL verification, we return success.
   return true;
 }
 
 void CertificateChecker::NotifyCertificateChecked(
+    ServerToCheck server_to_check,
     CertificateCheckResult result) {
   if (observer_)
-    observer_->CertificateChecked(server_to_check_, result);
+    observer_->CertificateChecked(server_to_check, result);
 }
 
 }  // namespace chromeos_update_engine
diff --git a/common/certificate_checker.h b/common/certificate_checker.h
index bc675be..c785192 100644
--- a/common/certificate_checker.h
+++ b/common/certificate_checker.h
@@ -78,6 +78,9 @@
 enum class ServerToCheck {
   kUpdate = 0,
   kDownload,
+
+  // Ignore this server.
+  kNone,
 };
 
 // Responsible for checking whether update server certificates change, and
@@ -96,10 +99,8 @@
                                     CertificateCheckResult result) = 0;
   };
 
-  CertificateChecker(PrefsInterface* prefs,
-                     OpenSSLWrapper* openssl_wrapper,
-                     ServerToCheck server_to_check);
-  virtual ~CertificateChecker() = default;
+  CertificateChecker(PrefsInterface* prefs, OpenSSLWrapper* openssl_wrapper);
+  ~CertificateChecker();
 
   // This callback is called by libcurl just before the initialization of an
   // SSL connection after having processed all other SSL related options. Used
@@ -109,6 +110,11 @@
                                     SSL_CTX* ssl_ctx,
                                     void* cert_checker);
 
+  // Initialize this class as the singleton instance. Only one instance can be
+  // initialized at a time and it should be initialized before other methods
+  // can be used.
+  void Init();
+
   // Set the certificate observer to the passed instance. To remove the
   // observer, pass a nullptr. The |observer| instance must be valid while this
   // CertificateChecker verifies certificates.
@@ -120,24 +126,37 @@
   FRIEND_TEST(CertificateCheckerTest, ChangedCertificate);
   FRIEND_TEST(CertificateCheckerTest, FailedCertificate);
 
-  // This callback is called by openssl after initial SSL verification. It is
-  // used to perform any additional security verification on the connection,
-  // but we use them here to get hold of the server certificate, in order to
-  // determine if it has changed since the last connection. Since openssl forces
-  // us to do this statically, we pass a pointer to this instance via a
-  // thread-safe global pointer. The assigned callback is then called once per
+  // These callbacks are asynchronously called by openssl after initial SSL
+  // verification. They are used to perform any additional security verification
+  // on the connection, but we use them here to get hold of the server
+  // certificate, in order to determine if it has changed since the last
+  // connection. Since openssl forces us to do this statically, we define two
+  // different callbacks for the two different official update servers, and only
+  // assign the correspondent one. The assigned callback is then called once per
   // each certificate on the server and returns 1 for success and 0 for failure.
-  static int VerifySSLCallback(int preverify_ok, X509_STORE_CTX* x509_ctx);
+  static int VerifySSLCallbackDownload(int preverify_ok,
+                                       X509_STORE_CTX* x509_ctx);
+  static int VerifySSLCallbackUpdate(int preverify_ok,
+                                     X509_STORE_CTX* x509_ctx);
+  static int VerifySSLCallback(int preverify_ok,
+                               X509_STORE_CTX* x509_ctx,
+                               ServerToCheck server_to_check);
 
   // Checks if server certificate stored in |x509_ctx| has changed since last
-  // connection to that same server, specified by the |server_to_check_| member.
+  // connection to that same server, specified by |server_to_check|.
   // This is called by the callbacks defined above. The result of the
   // certificate check is passed to the observer, if any. Returns true on
   // success and false otherwise.
-  bool CheckCertificateChange(int preverify_ok, X509_STORE_CTX* x509_ctx);
+  bool CheckCertificateChange(int preverify_ok,
+                              X509_STORE_CTX* x509_ctx,
+                              ServerToCheck server_to_check);
 
   // Notifies the observer, if any, of a certificate checking.
-  void NotifyCertificateChecked(CertificateCheckResult result);
+  void NotifyCertificateChecked(ServerToCheck server_to_check,
+                                CertificateCheckResult result);
+
+  // The CertificateChecker singleton instance.
+  static CertificateChecker* cert_checker_singleton_;
 
   // Prefs instance used to store the certificates seen in the past.
   PrefsInterface* prefs_;
@@ -145,9 +164,6 @@
   // The wrapper for openssl operations.
   OpenSSLWrapper* openssl_wrapper_;
 
-  // The server to check from this certificate checker instance.
-  ServerToCheck server_to_check_;
-
   // The observer called whenever a certificate is checked, if not null.
   Observer* observer_{nullptr};
 
diff --git a/common/certificate_checker_unittest.cc b/common/certificate_checker_unittest.cc
index 15811c0..c30acc5 100644
--- a/common/certificate_checker_unittest.cc
+++ b/common/certificate_checker_unittest.cc
@@ -50,6 +50,7 @@
                                    cert_key_prefix_.c_str(),
                                    static_cast<int>(server_to_check_),
                                    depth_);
+    cert_checker.Init();
     cert_checker.SetObserver(&observer_);
   }
 
@@ -70,7 +71,7 @@
   string cert_key_;
 
   testing::StrictMock<MockCertificateCheckObserver> observer_;
-  CertificateChecker cert_checker{&prefs_, &openssl_wrapper_, server_to_check_};
+  CertificateChecker cert_checker{&prefs_, &openssl_wrapper_};
 };
 
 // check certificate change, new
@@ -86,7 +87,8 @@
   EXPECT_CALL(observer_,
               CertificateChecked(server_to_check_,
                                  CertificateCheckResult::kValid));
-  ASSERT_TRUE(cert_checker.CheckCertificateChange(1, nullptr));
+  ASSERT_TRUE(
+      cert_checker.CheckCertificateChange(1, nullptr, server_to_check_));
 }
 
 // check certificate change, unchanged
@@ -103,7 +105,8 @@
   EXPECT_CALL(observer_,
               CertificateChecked(server_to_check_,
                                  CertificateCheckResult::kValid));
-  ASSERT_TRUE(cert_checker.CheckCertificateChange(1, nullptr));
+  ASSERT_TRUE(
+      cert_checker.CheckCertificateChange(1, nullptr, server_to_check_));
 }
 
 // check certificate change, changed
@@ -120,7 +123,8 @@
               CertificateChecked(server_to_check_,
                                  CertificateCheckResult::kValidChanged));
   EXPECT_CALL(prefs_, SetString(cert_key_, digest_hex_)).WillOnce(Return(true));
-  ASSERT_TRUE(cert_checker.CheckCertificateChange(1, nullptr));
+  ASSERT_TRUE(
+      cert_checker.CheckCertificateChange(1, nullptr, server_to_check_));
 }
 
 // check certificate change, failed
@@ -129,7 +133,8 @@
                                             CertificateCheckResult::kFailed));
   EXPECT_CALL(prefs_, GetString(_, _)).Times(0);
   EXPECT_CALL(openssl_wrapper_, GetCertificateDigest(_, _, _, _)).Times(0);
-  ASSERT_FALSE(cert_checker.CheckCertificateChange(0, nullptr));
+  ASSERT_FALSE(
+      cert_checker.CheckCertificateChange(0, nullptr, server_to_check_));
 }
 
 }  // namespace chromeos_update_engine
diff --git a/common/libcurl_http_fetcher.cc b/common/libcurl_http_fetcher.cc
index 51643a4..13784fa 100644
--- a/common/libcurl_http_fetcher.cc
+++ b/common/libcurl_http_fetcher.cc
@@ -44,13 +44,9 @@
 const int kNoNetworkRetrySeconds = 10;
 }  // namespace
 
-LibcurlHttpFetcher::LibcurlHttpFetcher(
-    ProxyResolver* proxy_resolver,
-    HardwareInterface* hardware,
-    std::unique_ptr<CertificateChecker> certificate_checker)
-  : HttpFetcher(proxy_resolver),
-    hardware_(hardware),
-    certificate_checker_(std::move(certificate_checker)) {
+LibcurlHttpFetcher::LibcurlHttpFetcher(ProxyResolver* proxy_resolver,
+                                       HardwareInterface* hardware)
+    : HttpFetcher(proxy_resolver), hardware_(hardware) {
   // Dev users want a longer timeout (180 seconds) because they may
   // be waiting on the dev server to build an image.
   if (!hardware_->IsOfficialBuild())
@@ -237,10 +233,10 @@
            CURLE_OK);
   CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_CIPHER_LIST, "HIGH:!ADH"),
            CURLE_OK);
-  if (certificate_checker_ != nullptr) {
-    CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_CTX_DATA,
-                              certificate_checker_.get()),
-             CURLE_OK);
+  if (server_to_check_ != ServerToCheck::kNone) {
+    CHECK_EQ(
+        curl_easy_setopt(curl_handle_, CURLOPT_SSL_CTX_DATA, &server_to_check_),
+        CURLE_OK);
     CHECK_EQ(curl_easy_setopt(curl_handle_, CURLOPT_SSL_CTX_FUNCTION,
                               CertificateChecker::ProcessSSLContext),
              CURLE_OK);
diff --git a/common/libcurl_http_fetcher.h b/common/libcurl_http_fetcher.h
index df0a7be..900c973 100644
--- a/common/libcurl_http_fetcher.h
+++ b/common/libcurl_http_fetcher.h
@@ -40,11 +40,7 @@
 class LibcurlHttpFetcher : public HttpFetcher {
  public:
   LibcurlHttpFetcher(ProxyResolver* proxy_resolver,
-                     HardwareInterface* hardware,
-                     std::unique_ptr<CertificateChecker> certificate_checker);
-  LibcurlHttpFetcher(ProxyResolver* proxy_resolver,
-                     HardwareInterface* hardware)
-      : LibcurlHttpFetcher(proxy_resolver, hardware, nullptr) {}
+                     HardwareInterface* hardware);
 
   // Cleans up all internal state. Does not notify delegate
   ~LibcurlHttpFetcher() override;
@@ -85,6 +81,10 @@
     no_network_max_retries_ = retries;
   }
 
+  void set_server_to_check(ServerToCheck server_to_check) {
+    server_to_check_ = server_to_check;
+  }
+
   size_t GetBytesDownloaded() override {
     return static_cast<size_t>(bytes_downloaded_);
   }
@@ -231,9 +231,10 @@
   // if we get a terminate request, queue it until we can handle it.
   bool terminate_requested_{false};
 
-  // The CertificateChecker used to check this connection's certificate. If no
-  // certificate check needs to be performed, this should be empty.
-  std::unique_ptr<CertificateChecker> certificate_checker_;
+  // The ServerToCheck used when checking this connection's certificate. If no
+  // certificate check needs to be performed, this should be set to
+  // ServerToCheck::kNone.
+  ServerToCheck server_to_check_{ServerToCheck::kNone};
 
   int low_speed_limit_bps_{kDownloadLowSpeedLimitBps};
   int low_speed_time_seconds_{kDownloadLowSpeedTimeSeconds};