diff --git a/letsencrypt/client/crypto_util.py b/letsencrypt/client/crypto_util.py
index bf9989495..554ccf684 100644
--- a/letsencrypt/client/crypto_util.py
+++ b/letsencrypt/client/crypto_util.py
@@ -148,7 +148,7 @@ def csr_matches_pubkey(csr, privkey):
 def make_key(bits=CONFIG.RSA_KEY_SIZE):
     """Generate PEM encoded RSA key.
 
-    :param int bits: Number of bits.
+    :param int bits: Number of bits, at least 1024.
 
     :returns: new RSA key in PEM form with specified number of bits
     :rtype: str
diff --git a/letsencrypt/client/tests/crypto_util_test.py b/letsencrypt/client/tests/crypto_util_test.py
index 272555d80..ac4b59d37 100644
--- a/letsencrypt/client/tests/crypto_util_test.py
+++ b/letsencrypt/client/tests/crypto_util_test.py
@@ -112,6 +112,14 @@ class CSRMatchesPubkeyTest(unittest.TestCase):
         self.assertFalse(self._call_testdata('csr.pem', RSA512_KEY))
 
 
+class MakeKeyTest(unittest.TestCase):
+    """Tests for letsencrypt.client.crypto_util.make_key."""
+
+    def test_it(self):
+        from letsencrypt.client.crypto_util import make_key
+        M2Crypto.RSA.load_key_string(make_key(1024))
+
+
 class ValidPrivkeyTest(unittest.TestCase):
     """Tests for letsencrypt.client.crypto_util.valid_privkey."""