diff --git a/common/utils.c b/common/utils.c
index ad938409..f2a10ccc 100644
--- a/common/utils.c
+++ b/common/utils.c
@@ -638,7 +638,7 @@ static int fls64(u64 x)
 	return 64 - i;
 }
 
-u64 parse_size(char *s)
+u64 parse_size(const char *s)
 {
 	char c;
 	char *endptr;
diff --git a/common/utils.h b/common/utils.h
index 7867fb0a..0ef1d6e8 100644
--- a/common/utils.h
+++ b/common/utils.h
@@ -65,7 +65,7 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_bytes, unsigned unit_mo
 #define pretty_size(size) 	pretty_size_mode(size, UNITS_DEFAULT)
 const char *pretty_size_mode(u64 size, unsigned mode);
 
-u64 parse_size(char *s);
+u64 parse_size(const char *s);
 u64 parse_qgroupid(const char *p);
 u64 arg_strtou64(const char *str);
 int open_file_or_dir(const char *fname, DIR **dirstream);