diff --git a/x509-cert/src/ext/pkix/crl.rs b/x509-cert/src/ext/pkix/crl.rs
index 5516fbc9e..f3e9397ba 100644
--- a/x509-cert/src/ext/pkix/crl.rs
+++ b/x509-cert/src/ext/pkix/crl.rs
@@ -45,6 +45,7 @@ impl AssociatedOid for BaseCrlNumber {
 }
 
 impl_newtype!(BaseCrlNumber, Uint);
+impl_extension!(BaseCrlNumber, critical = true);
 
 /// CrlDistributionPoints as defined in [RFC 5280 Section 4.2.1.13].
 ///
@@ -117,3 +118,5 @@ pub enum CrlReason {
 impl AssociatedOid for CrlReason {
     const OID: ObjectIdentifier = ID_CE_CRL_REASONS;
 }
+
+impl_extension!(CrlReason, critical = false);
diff --git a/x509-cert/src/ext/pkix/crl/dp.rs b/x509-cert/src/ext/pkix/crl/dp.rs
index 3b4764444..7acd2c95d 100644
--- a/x509-cert/src/ext/pkix/crl/dp.rs
+++ b/x509-cert/src/ext/pkix/crl/dp.rs
@@ -64,6 +64,8 @@ impl AssociatedOid for IssuingDistributionPoint {
     const OID: ObjectIdentifier = ID_PE_SUBJECT_INFO_ACCESS;
 }
 
+impl_extension!(IssuingDistributionPoint, critical = true);
+
 /// DistributionPoint as defined in [RFC 5280 Section 4.2.1.13].
 ///
 /// ```text
diff --git a/x509-cert/src/ext/pkix/keyusage.rs b/x509-cert/src/ext/pkix/keyusage.rs
index c15336218..833db69e6 100644
--- a/x509-cert/src/ext/pkix/keyusage.rs
+++ b/x509-cert/src/ext/pkix/keyusage.rs
@@ -188,6 +188,8 @@ impl AssociatedOid for PrivateKeyUsagePeriod {
     const OID: ObjectIdentifier = ID_CE_PRIVATE_KEY_USAGE_PERIOD;
 }
 
+impl_extension!(PrivateKeyUsagePeriod, critical = false);
+
 #[cfg(test)]
 mod tests {
     use super::*;