diff --git a/lib/cmdline.c b/lib/cmdline.c
index 5ba8a94..f5f3ad8 100644
--- a/lib/cmdline.c
+++ b/lib/cmdline.c
@@ -126,7 +126,7 @@
  *	megabyte, or one gigabyte, respectively.
  */
 
-unsigned long long memparse(char *ptr, char **retptr)
+unsigned long long memparse(const char *ptr, char **retptr)
 {
 	char *endptr;	/* local pointer to end of parsed string */