diff --git a/src/libopensc/pkcs15-pubkey.c b/src/libopensc/pkcs15-pubkey.c
index cd61eb05..c60e2c98 100644
--- a/src/libopensc/pkcs15-pubkey.c
+++ b/src/libopensc/pkcs15-pubkey.c
@@ -784,7 +784,7 @@ void sc_pkcs15_free_pubkey_info(sc_pkcs15_pubkey_info_t *key)
 	free(key);
 }
 
-int sc_pkcs15_read_der_file(sc_context_t *ctx, char * filename,
+static int sc_pkcs15_read_der_file(sc_context_t *ctx, char * filename,
 		u8 ** buf, size_t * buflen)
 {
 	int r;