diff --git a/src/BigDecimal.php b/src/BigDecimal.php
index d5a76ab..191ea26 100644
--- a/src/BigDecimal.php
+++ b/src/BigDecimal.php
@@ -447,7 +447,7 @@ final class BigDecimal extends BigNumber implements \Serializable
         $guess = $this->quotient($two);
         while (true) {
             $last = $guess;
-            $guess = $this->quotient($guess)->add($guess)->quotient($two);
+            $guess = $this->quotient($guess)->plus($guess)->quotient($two);
             // (($n / $guess) + $guess) / 2;
             if($last->compareTo($guess) == 0) {
                 break;
diff --git a/tests/BigDecimalTest.php b/tests/BigDecimalTest.php
index 22dd8c4..5c8aa5a 100644
--- a/tests/BigDecimalTest.php
+++ b/tests/BigDecimalTest.php
@@ -1372,7 +1372,7 @@ class BigDecimalTest extends AbstractTestCase
 
     public function testsqrt()
     {
-        $this->assertSame(BigDecimal::of(625)->sqrt(), BigDecimal::of(25));
+        $this->assertSame(BigDecimal::of(625)->sqrt()->compareTo(25), 0);
     }
 
     /**