diff --git a/src/proto.rs b/src/proto.rs
index 73bbd52..da0a989 100644
--- a/src/proto.rs
+++ b/src/proto.rs
@@ -237,7 +237,7 @@ mod tests {
             assert_eq!(
                 parse_result.err(),
                 Some(DNSParseError::DNSOpCodeInvalid),
-                "query: {:?}, opcode: {}",
+                "query: {:02x?}, opcode: {}",
                 dns_query,
                 opcode
             );
@@ -261,7 +261,11 @@ mod tests {
         for (idx, opcode) in valid_opcodes.iter().enumerate() {
             dns_query[2] = opcode << 3;
             let parse_result = DNSHeader::from_udp_datagram(&dns_query);
-            assert_eq!(parse_result?.opcode, valid_parsed_opcodes[idx]);
+            assert_eq!(
+                parse_result?.opcode, valid_parsed_opcodes[idx],
+                "query: {:02x?}, opcode: {}",
+                dns_query, opcode
+            );
         }
         Ok(())
     }