diff --git a/src/libopensc/pkcs15.c b/src/libopensc/pkcs15.c
index 373ec4c4..f63d8bf7 100644
--- a/src/libopensc/pkcs15.c
+++ b/src/libopensc/pkcs15.c
@@ -2097,8 +2097,7 @@ int
 sc_pkcs15_add_supported_algo_ref(struct sc_pkcs15_object *obj, 
 		struct sc_supported_algo_info *algo)
 {
-	int *algo_refs = NULL;
-	int ii;
+	unsigned int ii, *algo_refs = NULL;
 
 	if (!algo)
 		return SC_SUCCESS;
diff --git a/src/libopensc/pkcs15.h b/src/libopensc/pkcs15.h
index 9855db5c..31c04130 100644
--- a/src/libopensc/pkcs15.h
+++ b/src/libopensc/pkcs15.h
@@ -319,7 +319,7 @@ struct sc_pkcs15_prkey_info {
 	size_t modulus_length; /* RSA */
 	size_t field_length;   /* EC in bits */
 
-	int algo_refs[SC_MAX_SUPPORTED_ALGORITHMS];
+	unsigned int algo_refs[SC_MAX_SUPPORTED_ALGORITHMS];
 
 	struct sc_pkcs15_der subject;
 
@@ -338,7 +338,7 @@ struct sc_pkcs15_pubkey_info {
 	size_t modulus_length; /* RSA */
 	size_t field_length;   /* EC in bits */
 
-	int algo_refs[SC_MAX_SUPPORTED_ALGORITHMS];
+	unsigned int algo_refs[SC_MAX_SUPPORTED_ALGORITHMS];
 
 	struct sc_pkcs15_der subject;