diff --git a/test/bntest.c b/test/bntest.c
index 6f1f5d7cd9..96b1638d68 100644
--- a/test/bntest.c
+++ b/test/bntest.c
@@ -389,6 +389,54 @@ static int test_modexp_mont5(void)
     if (!TEST_BN_eq(c, d))
         goto err;
 
+    /* Regression test for carry bug in bn_sqrx8x_internal */
+    {
+        static const char *ahex[] = {
+                      "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8FFEADBCFC4DAE7FFF908E92820306B",
+            "9544D954000000006C0000000000000000000000000000000000000000000000",
+            "00000000000000000000FF030202FFFFF8FFEBDBCFC4DAE7FFF908E92820306B",
+            "9544D954000000006C000000FF0302030000000000FFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF01FC00FF02FFFFFFFF",
+            "00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00FCFD",
+            "FCFFFFFFFFFF000000000000000000FF0302030000000000FFFFFFFFFFFFFFFF",
+            "FF00FCFDFDFF030202FF00000000FFFFFFFFFFFFFFFFFF00FCFDFCFFFFFFFFFF",
+            NULL
+	};
+        static const char *nhex[] = {
+                      "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF8F8F8F8000000",
+            "00000010000000006C0000000000000000000000000000000000000000000000",
+            "00000000000000000000000000000000000000FFFFFFFFFFFFF8F8F8F8000000",
+            "00000010000000006C000000000000000000000000FFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "00FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFF000000000000000000000000000000000000FFFFFFFFFFFFFFFF",
+            "FFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+            NULL
+	};
+
+        bigstring = glue(ahex);
+        BN_hex2bn(&a, bigstring);
+        OPENSSL_free(bigstring);
+        bigstring = glue(nhex);
+        BN_hex2bn(&n, bigstring);
+        OPENSSL_free(bigstring);
+    }
+    BN_free(b);
+    b = BN_dup(a);
+    BN_MONT_CTX_set(mont, n, ctx);
+    BN_mod_mul_montgomery(c, a, a, mont, ctx);
+    BN_mod_mul_montgomery(d, a, b, mont, ctx);
+    if (!TEST_BN_eq(c, d))
+        goto err;
+
     /* Zero input */
     BN_bntest_rand(p, 1024, 0, 0);
     BN_zero(a);