diff --git a/src/util.c b/src/util.c
index 2832486d..3c6e2b1b 100644
--- a/src/util.c
+++ b/src/util.c
@@ -378,7 +378,7 @@ bool scan_freq_set_contains(const struct scan_freq_set *freqs, uint32_t freq)
 	return false;
 }
 
-uint32_t scan_freq_set_get_bands(struct scan_freq_set *freqs)
+uint32_t scan_freq_set_get_bands(const struct scan_freq_set *freqs)
 {
 	uint32_t bands = 0;
 	uint32_t max;
diff --git a/src/util.h b/src/util.h
index 75c29039..f61e3575 100644
--- a/src/util.h
+++ b/src/util.h
@@ -111,7 +111,7 @@ struct scan_freq_set *scan_freq_set_new(void);
 void scan_freq_set_free(struct scan_freq_set *freqs);
 bool scan_freq_set_add(struct scan_freq_set *freqs, uint32_t freq);
 bool scan_freq_set_contains(const struct scan_freq_set *freqs, uint32_t freq);
-uint32_t scan_freq_set_get_bands(struct scan_freq_set *freqs);
+uint32_t scan_freq_set_get_bands(const struct scan_freq_set *freqs);
 void scan_freq_set_foreach(const struct scan_freq_set *freqs,
 				scan_freq_set_func_t func, void *user_data);
 void scan_freq_set_merge(struct scan_freq_set *to,