diff --git a/libecdsaauth/keypair.c b/libecdsaauth/keypair.c
index 5e098c5..b5dd21e 100644
--- a/libecdsaauth/keypair.c
+++ b/libecdsaauth/keypair.c
@@ -22,6 +22,7 @@
 
 #include <string.h>
 #include <stdlib.h>
+#include <openssl/pem.h>
 
 static inline libecdsaauth_key_t *libecdsaauth_key_alloc(void)
 {
diff --git a/tool/main.c b/tool/main.c
index 23d19a3..f88016c 100644
--- a/tool/main.c
+++ b/tool/main.c
@@ -21,6 +21,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <openssl/pem.h>
 
 #include "libecdsaauth/keypair.h"
 #include "libecdsaauth/op.h"
@@ -41,7 +42,7 @@ static int tool_keygen(int argc, const char *argv[])
 	key = libecdsaauth_key_new();
 
 	pubout = fopen(argv[1], "w");
-	PEM_write_ECPrivateKey(pubout, key->eckey, NULL, NULL, 0, NULL);
+	PEM_write_ECPrivateKey(pubout, key->eckey, NULL, NULL, 0, NULL, NULL);
 	fclose(pubout);
 
 	pubkey = libecdsaauth_key_public_key_base64(key);