diff --git a/fuzz/cert.cc b/fuzz/cert.cc
index 4078c0ec..e813ed56 100644
--- a/fuzz/cert.cc
+++ b/fuzz/cert.cc
@@ -1,11 +1,17 @@
+#include <openssl/mem.h>
 #include <openssl/x509.h>
 
 extern "C" int LLVMFuzzerTestOneInput(uint8_t *buf, size_t len) {
   const uint8_t *bufp = buf;
   X509 *x509 = d2i_X509(NULL, &bufp, len);
   if (x509 != NULL) {
-    /* Also extract the public key. */
+    /* Extract the public key. */
     EVP_PKEY_free(X509_get_pubkey(x509));
+
+    /* Reserialize the structure. */
+    uint8_t *der = NULL;
+    i2d_X509(x509, &der);
+    OPENSSL_free(der);
   }
   X509_free(x509);
   return 0;