diff --git a/src/Utils.php b/src/Utils.php
index 387656f..2627fcc 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -172,8 +172,10 @@ class Utils
         } elseif (is_string($number)) {
             if (self::isZeroPrefixed($number)) {
                 $number = self::stripZero($number);
+                $bn = new BigNumber($number, 16);
+            } else {
+                $bn = new BigNumber($number);
             }
-            $bn = new BigNumber($number, 16);
         } elseif (!$number instanceof BigNumber){
             throw new InvalidArgumentException('toWei number must be BigNumber, string or int.');
         }
diff --git a/test/unit/UtilsTest.php b/test/unit/UtilsTest.php
index 3b49dde..7e1ea6c 100644
--- a/test/unit/UtilsTest.php
+++ b/test/unit/UtilsTest.php
@@ -122,14 +122,18 @@ class UtilsTest extends TestCase
 
         $this->assertEquals($bn->toString(), '1');
 
-        $bn = Utils::toWei('1', 'wei');
+        $bn = Utils::toWei('18', 'wei');
 
-        $this->assertEquals($bn->toString(), '1');
+        $this->assertEquals($bn->toString(), '18');
 
         $bn = Utils::toWei(1, 'wei');
 
         $this->assertEquals($bn->toString(), '1');
 
+        $bn = Utils::toWei(0x11, 'wei');
+
+        $this->assertEquals($bn->toString(), '17');
+
         $bn = Utils::toWei('1', 'ether');
 
         $this->assertEquals($bn->toString(), '1000000000000000000');
@@ -151,16 +155,21 @@ class UtilsTest extends TestCase
         $this->assertEquals($bnq->toString(), '0');
         $this->assertEquals($bnr->toString(), '1');
 
-        list($bnq, $bnr) = Utils::toEther('1', 'wei');
+        list($bnq, $bnr) = Utils::toEther('18', 'wei');
 
         $this->assertEquals($bnq->toString(), '0');
-        $this->assertEquals($bnr->toString(), '1');
+        $this->assertEquals($bnr->toString(), '18');
 
         list($bnq, $bnr) = Utils::toEther(1, 'wei');
 
         $this->assertEquals($bnq->toString(), '0');
         $this->assertEquals($bnr->toString(), '1');
 
+        list($bnq, $bnr) = Utils::toEther(0x11, 'wei');
+
+        $this->assertEquals($bnq->toString(), '0');
+        $this->assertEquals($bnr->toString(), '17');
+
         list($bnq, $bnr) = Utils::toEther('1', 'kether');
 
         $this->assertEquals($bnq->toString(), '1000');