diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 1f21a313..d2749ad3 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -326,9 +326,12 @@ class BigInteger
 
         switch ( MATH_BIGINTEGER_MODE ) {
             case MATH_BIGINTEGER_MODE_GMP:
-                if (is_resource($x) && get_resource_type($x) == 'GMP integer') {
-                    $this->value = $x;
-                    return;
+                switch (true) {
+                    case is_resource($x) && get_resource_type($x) == 'GMP integer':
+                    // PHP 5.6 switched GMP from using resources to objects
+                    case is_object($x) && get_class($x) == 'GMP':
+                        $this->value = $x;
+                        return;
                 }
                 $this->value = gmp_init(0);
                 break;