diff --git a/include/osmocore/bitvec.h b/include/osmocore/bitvec.h
index 11cb01e..7a26bce 100644
--- a/include/osmocore/bitvec.h
+++ b/include/osmocore/bitvec.h
@@ -40,10 +40,10 @@
 };
 
 /* check if the bit is 0 or 1 for a given position inside a bitvec */
-enum bit_value bitvec_get_bit_pos(struct bitvec *bv, unsigned int bitnr);
+enum bit_value bitvec_get_bit_pos(const struct bitvec *bv, unsigned int bitnr);
 
 /* get the Nth set bit inside the bit vector */
-unsigned int bitvec_get_nth_set_bit(struct bitvec *bv, unsigned int n);
+unsigned int bitvec_get_nth_set_bit(const struct bitvec *bv, unsigned int n);
 
 /* Set a bit at given position */
 int bitvec_set_bit_pos(struct bitvec *bv, unsigned int bitnum,