diff --git a/tinyldap.c b/tinyldap.c
index 0291e0f..a8d7de1 100644
--- a/tinyldap.c
+++ b/tinyldap.c
@@ -204,7 +204,7 @@ static void fixupadl(struct AttributeDescriptionList* a) {
 
 uint32 filters,acls;		/* number of filters and acls in the ACL section of the data file */
 uint32 filtertab,acltab;	/* offsets of the filter and acl table in the data file */
-char* acl_ec_subjects;		/* if the n'th byte here is nonzero, then the current subject
+signed char* acl_ec_subjects;		/* if the n'th byte here is nonzero, then the current subject
 				   (the dn the user is logged in as) matches the n'th filter, i.e.
 				   the ACLs with this subject need to be applied. */
 struct Filter** Filters;