diff --git a/OpenVPN Adapter/OpenVPNCertificate.h b/OpenVPN Adapter/OpenVPNCertificate.h
index 57d2f9c..22408d0 100644
--- a/OpenVPN Adapter/OpenVPNCertificate.h	
+++ b/OpenVPN Adapter/OpenVPNCertificate.h	
@@ -15,6 +15,8 @@ NS_ASSUME_NONNULL_BEGIN
 + (nullable OpenVPNCertificate *)certificateWithPEM:(NSData *)pemData error:(NSError **)error;
 + (nullable OpenVPNCertificate *)certificateWithDER:(NSData *)derData error:(NSError **)error;
 
+@property (readonly, nonatomic) NSData *serial;
+
 - (instancetype) init NS_UNAVAILABLE;
 
 - (nullable NSData *)pemData:(NSError **)error;
diff --git a/OpenVPN Adapter/OpenVPNCertificate.m b/OpenVPN Adapter/OpenVPNCertificate.m
index 907843c..1400f77 100644
--- a/OpenVPN Adapter/OpenVPNCertificate.m	
+++ b/OpenVPN Adapter/OpenVPNCertificate.m	
@@ -9,6 +9,7 @@
 
 #include <mbedtls/x509_crt.h>
 #include <mbedtls/pem.h>
+#include <mbedtls/bignum.h>
 
 #import "NSError+OpenVPNError.h"
 
@@ -52,6 +53,10 @@
     return certificate;
 }
 
+- (NSData *)serial {
+    return [NSData dataWithBytes:self.crt->serial.p length:self.crt->serial.len];
+}
+
 - (instancetype)init
 {
     if (self = [super init]) {