diff --git a/STYLE b/STYLE
index cb2d297e..578da68c 100644
--- a/STYLE
+++ b/STYLE
@@ -105,7 +105,8 @@ type.
 Some types are allocated within the library while others are
 initialized into a struct allocated by the caller, often on the
 stack. Name these functions TYPE_NAME_new/TYPE_NAME_free and
-TYPE_NAME_init/TYPE_NAME_cleanup, respectively.
+TYPE_NAME_init/TYPE_NAME_cleanup, respectively. All TYPE_NAME_free
+functions must do nothing on NULL input.
 
 If a variable is the length of a pointer value, it has the suffix
 _len. An output parameter is named out or has an out_ prefix. For
diff --git a/crypto/x509/x509_vpm.c b/crypto/x509/x509_vpm.c
index cf4283dc..8c8f98ea 100644
--- a/crypto/x509/x509_vpm.c
+++ b/crypto/x509/x509_vpm.c
@@ -185,6 +185,8 @@ X509_VERIFY_PARAM *X509_VERIFY_PARAM_new(void)
 
 void X509_VERIFY_PARAM_free(X509_VERIFY_PARAM *param)
 	{
+	if (param == NULL)
+		return;
 	x509_verify_param_zero(param);
 	OPENSSL_free(param->id);
 	OPENSSL_free(param);
diff --git a/ssl/d1_both.c b/ssl/d1_both.c
index 4e084af7..ec2d920d 100644
--- a/ssl/d1_both.c
+++ b/ssl/d1_both.c
@@ -196,6 +196,9 @@ static hm_fragment *dtls1_hm_fragment_new(unsigned long frag_len,
 }
 
 void dtls1_hm_fragment_free(hm_fragment *frag) {
+  if (frag == NULL) {
+    return;
+  }
   if (frag->fragment) {
     OPENSSL_free(frag->fragment);
   }
diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 348c7a8f..2d0bec70 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -460,6 +460,9 @@ int SSL_set1_param(SSL *ssl, X509_VERIFY_PARAM *vpm) {
 
 void ssl_cipher_preference_list_free(
     struct ssl_cipher_preference_list_st *cipher_list) {
+  if (cipher_list == NULL) {
+    return;
+  }
   sk_SSL_CIPHER_free(cipher_list->ciphers);
   OPENSSL_free(cipher_list->in_group_flags);
   OPENSSL_free(cipher_list);