diff --git a/src/cfdp/pdu/eof.rs b/src/cfdp/pdu/eof.rs
index 71f977b..16f2bba 100644
--- a/src/cfdp/pdu/eof.rs
+++ b/src/cfdp/pdu/eof.rs
@@ -106,7 +106,7 @@ impl EofPdu {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::EofPdu))
+            PduError::InvalidDirectiveType((buf[current_idx], Some(FileDirectiveType::EofPdu)))
         })?;
         if directive_type != FileDirectiveType::EofPdu {
             return Err(PduError::WrongDirectiveType((
diff --git a/src/cfdp/pdu/finished.rs b/src/cfdp/pdu/finished.rs
index 29cf747..463ca8d 100644
--- a/src/cfdp/pdu/finished.rs
+++ b/src/cfdp/pdu/finished.rs
@@ -170,7 +170,7 @@ impl<'fs_responses> FinishedPdu<'fs_responses> {
         let min_expected_len = current_idx + 2;
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::FinishedPdu))
+            PduError::InvalidDirectiveType((buf[current_idx], Some(FileDirectiveType::FinishedPdu)))
         })?;
         if directive_type != FileDirectiveType::FinishedPdu {
             return Err(PduError::WrongDirectiveType((
diff --git a/src/cfdp/pdu/metadata.rs b/src/cfdp/pdu/metadata.rs
index 2e3b5f0..fe2e4d2 100644
--- a/src/cfdp/pdu/metadata.rs
+++ b/src/cfdp/pdu/metadata.rs
@@ -248,7 +248,7 @@ impl<'src_name, 'dest_name, 'opts> MetadataPdu<'src_name, 'dest_name, 'opts> {
         }
         generic_length_checks_pdu_deserialization(buf, min_expected_len, full_len_without_crc)?;
         let directive_type = FileDirectiveType::try_from(buf[current_idx]).map_err(|_| {
-            PduError::InvalidDirectiveType((buf[current_idx], FileDirectiveType::MetadataPdu))
+            PduError::InvalidDirectiveType((buf[current_idx], Some(FileDirectiveType::MetadataPdu)))
         })?;
         if directive_type != FileDirectiveType::MetadataPdu {
             return Err(PduError::WrongDirectiveType((
diff --git a/src/cfdp/pdu/mod.rs b/src/cfdp/pdu/mod.rs
index d015d99..729a88a 100644
--- a/src/cfdp/pdu/mod.rs
+++ b/src/cfdp/pdu/mod.rs
@@ -43,8 +43,8 @@ pub enum PduError {
     WrongDirectiveType((FileDirectiveType, FileDirectiveType)),
     /// The directive type field contained a value not in the range of permitted values.
     /// The first tuple entry will be the found raw number, the second entry the expected entry
-    /// type.
-    InvalidDirectiveType((u8, FileDirectiveType)),
+    /// type when applicable.
+    InvalidDirectiveType((u8, Option<FileDirectiveType>)),
     /// Invalid condition code. Contains the raw detected value.
     InvalidConditionCode(u8),
     /// Invalid checksum type which is not part of the checksums listed in the
@@ -101,8 +101,7 @@ impl Display for PduError {
             PduError::InvalidDirectiveType((found, expected)) => {
                 write!(
                     f,
-                    "invalid directive type value {found}, expected {expected:?} ({})",
-                    *expected as u8
+                    "invalid directive type value {found}, expected {expected:?}"
                 )
             }
             PduError::InvalidChecksumType(checksum_type) => {