diff --git a/src/libopensc/pkcs15-prkey.c b/src/libopensc/pkcs15-prkey.c
index ed0ce6b4..6ec339b9 100644
--- a/src/libopensc/pkcs15-prkey.c
+++ b/src/libopensc/pkcs15-prkey.c
@@ -606,6 +606,9 @@ sc_pkcs15_free_prkey(struct sc_pkcs15_prkey *key)
 
 void sc_pkcs15_free_prkey_info(sc_pkcs15_prkey_info_t *key)
 {
+	if (!key)
+		return;
+
 	if (key->subject.value)
 		free(key->subject.value);