diff --git a/fuzz/cert.cc b/fuzz/cert.cc
index ad40a31..4078c0e 100644
--- a/fuzz/cert.cc
+++ b/fuzz/cert.cc
@@ -2,6 +2,11 @@
 
 extern "C" int LLVMFuzzerTestOneInput(uint8_t *buf, size_t len) {
   const uint8_t *bufp = buf;
-  X509_free(d2i_X509(NULL, &bufp, len));
+  X509 *x509 = d2i_X509(NULL, &bufp, len);
+  if (x509 != NULL) {
+    /* Also extract the public key. */
+    EVP_PKEY_free(X509_get_pubkey(x509));
+  }
+  X509_free(x509);
   return 0;
 }