battery plugin: constify

diff --git a/src/battery.c b/src/battery.c
index c4c050d..b87739a 100644 (file)
--- a/src/battery.c
+++ b/src/battery.c
@@ -143,7 +143,7 @@ static void submit_capacity (char const *plugin_instance, /* {{{ */
 } /* }}} void submit_capacity */
 
 #if HAVE_IOKIT_PS_IOPOWERSOURCES_H || HAVE_IOKIT_IOKITLIB_H
-static double dict_get_double (CFDictionaryRef dict, char *key_string) /* {{{ */
+static double dict_get_double (CFDictionaryRef dict, const char *key_string) /* {{{ */
 {
        double      val_double;
        long long   val_int;