diff --git a/src/Firebase.cpp b/src/Firebase.cpp
index fcf32993..92b465c4 100644
--- a/src/Firebase.cpp
+++ b/src/Firebase.cpp
@@ -33,8 +33,8 @@ std::string makeFirebaseURL(const std::string& path, const std::string& auth) {
 
 }  // namespace
 
-Firebase::Firebase(const std::string& host, const std::string& auth) : host_(host), auth_(auth) {
-  http_.reset(FirebaseHttpClient::create());
+Firebase::Firebase(WiFiClient* client, const std::string& host, const std::string& auth) : host_(host), auth_(auth) {
+  http_.reset(FirebaseHttpClient::create(client));
   http_->setReuseConnection(true);
 }
 
diff --git a/src/Firebase.h b/src/Firebase.h
index 44450557..2e5d6db2 100644
--- a/src/Firebase.h
+++ b/src/Firebase.h
@@ -32,7 +32,7 @@
 // Firebase REST API client.
 class Firebase {
  public:
-  Firebase(const std::string& host, const std::string& auth = "");
+  Firebase(WiFiClient* client, const std::string& host, const std::string& auth = "");
 
   const std::string& auth() const;
 
diff --git a/src/FirebaseArduino.cpp b/src/FirebaseArduino.cpp
index bae29595..f8314380 100644
--- a/src/FirebaseArduino.cpp
+++ b/src/FirebaseArduino.cpp
@@ -19,14 +19,15 @@
 // This is needed to compile std::string on esp8266.
 template class std::basic_string<char>;
 
-void FirebaseArduino::begin(const String& host, const String& auth) {
+void FirebaseArduino::begin(WiFiClient* client, const String& host, const String& auth) {
   host_ = host.c_str();
   auth_ = auth.c_str();
+  client_ = client;
 }
 
 void FirebaseArduino::initStream() {
   if (stream_http_.get() == nullptr) {
-    stream_http_.reset(FirebaseHttpClient::create());
+    stream_http_.reset(FirebaseHttpClient::create(client_));
     stream_http_->setReuseConnection(true);
     stream_.reset(new FirebaseStream(stream_http_));
   }
@@ -34,7 +35,7 @@ void FirebaseArduino::initStream() {
 
 void FirebaseArduino::initRequest() {
   if (req_http_.get() == nullptr) {
-    req_http_.reset(FirebaseHttpClient::create());
+    req_http_.reset(FirebaseHttpClient::create(client_));
     req_http_->setReuseConnection(true);
     req_.reset(new FirebaseRequest(req_http_));
   }
@@ -197,8 +198,9 @@ bool FirebaseArduino::failed() {
   return error_.code() != 0;
 }
 
-const String& FirebaseArduino::error() {
-  return error_.message().c_str();
+void FirebaseArduino::error(std::string* buf) {
+    std::string err = error_.message();
+    *buf = err;
 }
 
 FirebaseArduino Firebase;
diff --git a/src/FirebaseArduino.h b/src/FirebaseArduino.h
index e2f264e1..b388e720 100644
--- a/src/FirebaseArduino.h
+++ b/src/FirebaseArduino.h
@@ -37,7 +37,7 @@ class FirebaseArduino {
    * \param host Your firebase db host, usually X.firebaseio.com.
    * \param auth Optional credentials for the db, a secret or token.
    */
-  virtual void begin(const String& host, const String& auth = "");
+  virtual void begin(WiFiClient* client, const String& host, const String& auth = "");
 
   /**
    * Appends the integer value to the node at path.
@@ -221,7 +221,8 @@ class FirebaseArduino {
   /**
    * \return Error message from last command if failed() is true.
    */
-  virtual const String& error();
+  virtual void error(std::string* buf);
+
  private:
   std::string host_;
   std::string auth_;
@@ -230,6 +231,7 @@ class FirebaseArduino {
   std::shared_ptr<FirebaseRequest> req_;
   std::shared_ptr<FirebaseHttpClient> stream_http_;
   std::shared_ptr<FirebaseStream> stream_;
+  WiFiClient* client_;
 
   void initStream();
   void initRequest();
diff --git a/src/FirebaseCloudMessaging.cpp b/src/FirebaseCloudMessaging.cpp
index e88727ab..e0ef8689 100644
--- a/src/FirebaseCloudMessaging.cpp
+++ b/src/FirebaseCloudMessaging.cpp
@@ -8,9 +8,10 @@ FirebaseCloudMessage FirebaseCloudMessage::SimpleNotification(
   return message;
 }
 
-FirebaseCloudMessaging::FirebaseCloudMessaging(const std::string& server_key) {
+FirebaseCloudMessaging::FirebaseCloudMessaging(WiFiClient* client, const std::string& server_key) {
   auth_header_ = "key=";
   auth_header_ += server_key;
+  client_ = client;
 }
 
 const FirebaseError FirebaseCloudMessaging::SendMessageToUser(
@@ -63,7 +64,7 @@ const FirebaseError FirebaseCloudMessaging::SendMessageToTopic(
 
 const FirebaseError FirebaseCloudMessaging::SendPayload(
     const char* payload) {
-  std::shared_ptr<FirebaseHttpClient> client(FirebaseHttpClient::create());
+  std::shared_ptr<FirebaseHttpClient> client(FirebaseHttpClient::create(client_));
   client->begin("http://fcm.googleapis.com/fcm/send");
   client->addHeader("Authorization", auth_header_.c_str());
   client->addHeader("Content-Type", "application/json");
diff --git a/src/FirebaseCloudMessaging.h b/src/FirebaseCloudMessaging.h
index 519946c6..db6d286a 100644
--- a/src/FirebaseCloudMessaging.h
+++ b/src/FirebaseCloudMessaging.h
@@ -64,7 +64,7 @@ struct FirebaseCloudMessage {
 // Firebase REST API client.
 class FirebaseCloudMessaging {
  public:
-  FirebaseCloudMessaging(const std::string& server_key);
+  FirebaseCloudMessaging(WiFiClient* client, const std::string& server_key);
   const FirebaseError SendMessageToUser(const std::string& registration_id,
                                         const FirebaseCloudMessage& message);
   const FirebaseError SendMessageToUsers(const std::vector<std::string>& registration_ids,
@@ -82,5 +82,6 @@ class FirebaseCloudMessaging {
   const void AddToJson(const FirebaseCloudMessage& message, JsonObject& json) const;
 
   std::string auth_header_;
+  WiFiClient* client_;
 };
 #endif  // firebase_cloud_messaging_h
diff --git a/src/FirebaseHttpClient.h b/src/FirebaseHttpClient.h
index 4b585aa6..c395b529 100644
--- a/src/FirebaseHttpClient.h
+++ b/src/FirebaseHttpClient.h
@@ -5,6 +5,7 @@
 
 #include "Arduino.h"
 #include "Stream.h"
+#include <WiFiClient.h>
 
 struct HttpStatus {
   static const int TEMPORARY_REDIRECT = 307;
@@ -12,7 +13,7 @@ struct HttpStatus {
 
 class FirebaseHttpClient {
  public:
-  static FirebaseHttpClient* create();
+  static FirebaseHttpClient* create(WiFiClient* client);
 
   virtual void setReuseConnection(bool reuse) = 0;
   virtual void begin(const std::string& url) = 0;
@@ -39,7 +40,4 @@ class FirebaseHttpClient {
   static const uint16_t kFirebasePort = 443;
 };
 
-static const char kFirebaseFingerprint[] =
-      "B6 F5 80 C8 B1 DA 61 C1 07 9D 80 42 D8 A9 1F AF 9F C8 96 7D"; // 2019-04
-
 #endif  // FIREBASE_HTTP_CLIENT_H
diff --git a/src/FirebaseHttpClient_Esp8266.cpp b/src/FirebaseHttpClient_Esp8266.cpp
index c78590dc..62a84e41 100644
--- a/src/FirebaseHttpClient_Esp8266.cpp
+++ b/src/FirebaseHttpClient_Esp8266.cpp
@@ -36,7 +36,9 @@ class ForceReuseHTTPClient : public HTTPClient {
 
 class FirebaseHttpClientEsp8266 : public FirebaseHttpClient {
  public:
-  FirebaseHttpClientEsp8266() {}
+  FirebaseHttpClientEsp8266(WiFiClient* client) {
+    client_ = client;
+  }
 
   void setReuseConnection(bool reuse) override {
     http_.setReuse(reuse);
@@ -44,11 +46,11 @@ class FirebaseHttpClientEsp8266 : public FirebaseHttpClient {
   }
 
   void begin(const std::string& url) override {
-    http_.begin(url.c_str(), kFirebaseFingerprint);
+    http_.begin(*client_, url.c_str());
   }
 
   void begin(const std::string& host, const std::string& path) override {
-    http_.begin(host.c_str(), kFirebasePort, path.c_str(), kFirebaseFingerprint);
+    http_.begin(*client_, host.c_str(), kFirebasePort, path.c_str());
   }
 
   void end() override {
@@ -89,9 +91,10 @@ class FirebaseHttpClientEsp8266 : public FirebaseHttpClient {
 
  private:
   ForceReuseHTTPClient http_;
+  WiFiClient* client_;
 };
 
-FirebaseHttpClient* FirebaseHttpClient::create() {
-  return new FirebaseHttpClientEsp8266();
+FirebaseHttpClient* FirebaseHttpClient::create(WiFiClient* client) {
+  return new FirebaseHttpClientEsp8266(client);
 }