diff --git a/test/openssl/test_bn.rb b/test/openssl/test_bn.rb
index 77af14091..ea88ff06c 100644
--- a/test/openssl/test_bn.rb
+++ b/test/openssl/test_bn.rb
@@ -175,7 +175,9 @@ def test_mod_sqr
   end
 
   def test_mod_sqrt
-    assert_equal(3, 4.to_bn.mod_sqrt(5))
+    assert_equal(4, 4.to_bn.mod_sqrt(5).mod_sqr(5))
+    # One of 189484 or 326277 is returned as a square root of 2 (mod 515761).
+    assert_equal(2, 2.to_bn.mod_sqrt(515761).mod_sqr(515761))
     assert_equal(0, 5.to_bn.mod_sqrt(5))
     assert_raise(OpenSSL::BNError) { 3.to_bn.mod_sqrt(5) }
   end