diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index a9b6f8b..b533b43 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -353,8 +353,8 @@
             encipher_only = self.encipher_only
             decipher_only = self.decipher_only
         except ValueError:
-            encipher_only = "N/A"
-            decipher_only = "N/A"
+            encipher_only = None
+            decipher_only = None
 
         return ("<KeyUsage(digital_signature={0.digital_signature}, "
                 "content_commitment={0.content_commitment}, "
diff --git a/tests/test_x509_ext.py b/tests/test_x509_ext.py
index acfe761..9f98bce 100644
--- a/tests/test_x509_ext.py
+++ b/tests/test_x509_ext.py
@@ -149,8 +149,8 @@
         assert repr(ku) == (
             "<KeyUsage(digital_signature=True, content_commitment=True, key_en"
             "cipherment=False, data_encipherment=False, key_agreement=False, k"
-            "ey_cert_sign=True, crl_sign=False, encipher_only=N/A, decipher_on"
-            "ly=N/A)>"
+            "ey_cert_sign=True, crl_sign=False, encipher_only=None, decipher_o"
+            "nly=None)>"
         )
 
     def test_repr_key_agreement_true(self):