diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index da79b031..1807e4aa 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -2727,7 +2727,14 @@ class Math_BigInteger
     {
         switch (MATH_BIGINTEGER_MODE) {
             case MATH_BIGINTEGER_MODE_GMP:
-                return gmp_cmp($this->value, $y->value);
+                $r = gmp_cmp($this->value, $y->value);
+                if ($r < -1) {
+                    $r = -1;
+                }
+                if ($r > 1) {
+                    $r = 1;
+                }
+                return $r;
             case MATH_BIGINTEGER_MODE_BCMATH:
                 return bccomp($this->value, $y->value, 0);
         }