diff --git a/lib/httprpc.js b/lib/httprpc.js
index c1ee0f02a..99f02b532 100644
--- a/lib/httprpc.js
+++ b/lib/httprpc.js
@@ -45,7 +45,8 @@ if(process.env.NODE_ENV !== "build") {
 
         return {
             _id: object.id,
-            data: object.result
+            data: object.result,
+            error: object.error
         };
     }
 
@@ -75,7 +76,7 @@ if(process.env.NODE_ENV !== "build") {
         var self = this;
         this.sendRequest(payload, function (request) {
             var parsed = JSON.parse(request.responseText);
-            if (parsed.result instanceof Array ? parsed.result.length === 0 : !parsed.result) {
+            if (parsed.error || (parsed.result instanceof Array ? parsed.result.length === 0 : !parsed.result)) {
                 return;
             }
             self.handlers.forEach(function (handler) {
diff --git a/lib/main.js b/lib/main.js
index 08eb722e2..5655a762e 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -155,15 +155,15 @@
                     return {call: call, args: args};
                 }).then(function (request) {
                     return new Promise(function (resolve, reject) {
-                        web3.provider.send(request, function (result) {
-                            if (result || typeof result === "boolean") {
+                        web3.provider.send(request, function (err, result) {
+                            if (!err) {
                                 resolve(result);
                                 return;
                             }
-                            reject(result);
+                            reject(err);
                         });
                     });
-                }).catch(function( err) {
+                }).catch(function(err) {
                     console.error(err);
                 });
             };
@@ -175,8 +175,12 @@
             var proto = {};
             proto.get = function () {
                 return new Promise(function(resolve, reject) {
-                    web3.provider.send({call: property.getter}, function(result) {
-                        resolve(result);
+                    web3.provider.send({call: property.getter}, function(err, result) {
+                        if (!err) {
+                            resolve(result);
+                            return;
+                        }
+                        reject(err);
                     });
                 });
             };
@@ -184,12 +188,12 @@
                 proto.set = function (val) {
                     return flattenPromise([val]).then(function (args) {
                         return new Promise(function (resolve) {
-                            web3.provider.send({call: property.setter, args: args}, function (result) {
-                                if (result) {
+                            web3.provider.send({call: property.setter, args: args}, function (err, result) {
+                                if (!err) {
                                     resolve(result);
-                                } else {
-                                    reject(result);
+                                    return;
                                 }
+                                reject(err);
                             });
                         });
                     }).catch(function (err) {
@@ -219,6 +223,8 @@
             // Find termination
             var str = "";
             var i = 0, l = hex.length;
+            if (hex.substring(0, 2) == '0x')
+                i = 2;
             for(; i < l; i+=2) {
                 var code = hex.charCodeAt(i);
                 if(code === 0) {
@@ -240,7 +246,8 @@
             var hex = this.toHex(str);
             while(hex.length < pad*2)
                 hex += "00";
-            return hex;
+
+            return "0x" + hex;
         },
 
         eth: {
@@ -440,7 +447,7 @@
         if(data._id) {
             var cb = web3._callbacks[data._id];
             if (cb) {
-                cb.call(this, data.data);
+                cb.call(this, data.error, data.data)
                 delete web3._callbacks[data._id];
             }
         }