diff --git a/src/cred.rs b/src/cred.rs
index 21518bf..010ad12 100644
--- a/src/cred.rs
+++ b/src/cred.rs
@@ -30,12 +30,16 @@ impl Credential {
 }
 
 impl CredentialRef {
-    pub fn aaguid(&self) -> &[u8] {
+    pub fn aaguid(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_aaguid_ptr(self.as_ptr()),
-                fido_cred_aaguid_len(self.as_ptr()),
-            )
+            if fido_cred_aaguid_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_aaguid_ptr(self.as_ptr()),
+                    fido_cred_aaguid_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -48,12 +52,16 @@ impl CredentialRef {
         }
     }
 
-    pub fn authdata(&self) -> &[u8] {
+    pub fn authdata(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_authdata_ptr(self.as_ptr()),
-                fido_cred_authdata_len(self.as_ptr()),
-            )
+            if fido_cred_authdata_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_authdata_ptr(self.as_ptr()),
+                    fido_cred_authdata_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -66,12 +74,16 @@ impl CredentialRef {
         }
     }
 
-    pub fn clientdata_hash(&self) -> &[u8] {
+    pub fn clientdata_hash(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_clientdata_hash_ptr(self.as_ptr()),
-                fido_cred_clientdata_hash_len(self.as_ptr()),
-            )
+            if fido_cred_clientdata_hash_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_clientdata_hash_ptr(self.as_ptr()),
+                    fido_cred_clientdata_hash_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -105,21 +117,29 @@ impl CredentialRef {
         }
     }
 
-    pub fn cred_id(&self) -> &[u8] {
+    pub fn cred_id(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_id_ptr(self.as_ptr()),
-                fido_cred_id_len(self.as_ptr()),
-            )
+            if fido_cred_id_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_id_ptr(self.as_ptr()),
+                    fido_cred_id_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
-    pub fn largeblob_key(&self) -> &[u8] {
+    pub fn largeblob_key(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_largeblob_key_ptr(self.as_ptr()),
-                fido_cred_largeblob_key_len(self.as_ptr()),
-            )
+            if fido_cred_largeblob_key_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_largeblob_key_ptr(self.as_ptr()),
+                    fido_cred_largeblob_key_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -145,12 +165,16 @@ impl CredentialRef {
         }
     }
 
-    pub fn pubkey(&self) -> &[u8] {
+    pub fn pubkey(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_pubkey_ptr(self.as_ptr()),
-                fido_cred_pubkey_len(self.as_ptr()),
-            )
+            if fido_cred_pubkey_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_pubkey_ptr(self.as_ptr()),
+                    fido_cred_pubkey_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -321,12 +345,16 @@ impl CredentialRef {
         unsafe { check(fido_cred_set_x509(self.as_ptr_mut(), &x509[0], x509.len())) }
     }
 
-    pub fn sig(&self) -> &[u8] {
+    pub fn sig(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_sig_ptr(self.as_ptr()),
-                fido_cred_sig_len(self.as_ptr()),
-            )
+            if fido_cred_sig_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_sig_ptr(self.as_ptr()),
+                    fido_cred_sig_len(self.as_ptr()),
+                ))
+            }
         }
     }
 
@@ -373,12 +401,16 @@ impl CredentialRef {
         unsafe { check(fido_cred_verify_self(self.as_ptr())) }
     }
 
-    pub fn x5c(&self) -> &[u8] {
+    pub fn x5c(&self) -> Option<&[u8]> {
         unsafe {
-            std::slice::from_raw_parts(
-                fido_cred_x5c_ptr(self.as_ptr()),
-                fido_cred_x5c_len(self.as_ptr()),
-            )
+            if fido_cred_x5c_ptr(self.as_ptr()).is_null() {
+                None
+            } else {
+                Some(std::slice::from_raw_parts(
+                    fido_cred_x5c_ptr(self.as_ptr()),
+                    fido_cred_x5c_len(self.as_ptr()),
+                ))
+            }
         }
     }
 }