diff --git a/openmls/src/ciphersuite/mac.rs b/openmls/src/ciphersuite/mac.rs
index 7e721bb458..5547e7a163 100644
--- a/openmls/src/ciphersuite/mac.rs
+++ b/openmls/src/ciphersuite/mac.rs
@@ -13,7 +13,7 @@ pub struct Mac {
 
 impl std::fmt::Debug for Mac {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", std::str::from_utf8(self.mac_value.as_slice()).unwrap_or_default())
+        write!(f, "{:x?}", self.mac_value.as_slice())
     }
 }
 
diff --git a/openmls/src/ciphersuite/signature.rs b/openmls/src/ciphersuite/signature.rs
index 228c28cbcd..7a463b262d 100644
--- a/openmls/src/ciphersuite/signature.rs
+++ b/openmls/src/ciphersuite/signature.rs
@@ -17,7 +17,7 @@ pub struct Signature {
 
 impl std::fmt::Debug for Signature {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", std::str::from_utf8(self.value.as_slice()).unwrap_or_default())
+        write!(f, "{:x?}", self.value.as_slice())
     }
 }
 
diff --git a/openmls/src/extensions/external_pub_extension.rs b/openmls/src/extensions/external_pub_extension.rs
index 8931924dd6..6067ae4aff 100644
--- a/openmls/src/extensions/external_pub_extension.rs
+++ b/openmls/src/extensions/external_pub_extension.rs
@@ -19,7 +19,7 @@ pub struct ExternalPubExtension {
 
 impl std::fmt::Debug for ExternalPubExtension {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", std::str::from_utf8(self.external_pub.as_slice()).unwrap_or_default())
+        write!(f, "{:x?}", self.external_pub.as_slice())
     }
 }