diff --git a/gvc-mixer-ui-device.c b/gvc-mixer-ui-device.c
index e36a69d..df2628e 100644
--- a/gvc-mixer-ui-device.c
+++ b/gvc-mixer-ui-device.c
@@ -308,7 +308,7 @@ get_profile_canonical_name (const gchar *profile_name, const gchar *skip_prefix)
 {
         gchar *result = NULL;
         gchar **s;
-        int i;
+        guint i;
 
         /* optimisation for the simple case. */
         if (strstr (profile_name, skip_prefix) == NULL)
@@ -338,7 +338,7 @@ get_profile_canonical_name (const gchar *profile_name, const gchar *skip_prefix)
 const gchar *
 gvc_mixer_ui_device_get_matching_profile (GvcMixerUIDevice *device, const gchar *profile)
 {
-        gchar *skip_prefix = device->priv->type == UIDeviceInput ? "output:" : "input:";
+        const gchar *skip_prefix = device->priv->type == UIDeviceInput ? "output:" : "input:";
         gchar *target_cname = get_profile_canonical_name (profile, skip_prefix);
         GList *l;
         gchar *result = NULL;
@@ -426,7 +426,7 @@ gvc_mixer_ui_device_set_profiles (GvcMixerUIDevice *device,
                                   const GList      *in_profiles)
 {
         GHashTable *added_profiles;
-        gchar *skip_prefix = device->priv->type == UIDeviceInput ? "output:" : "input:";
+        const gchar *skip_prefix = device->priv->type == UIDeviceInput ? "output:" : "input:";
 
         g_debug ("Set profiles for '%s'", gvc_mixer_ui_device_get_description(device));
 
@@ -463,7 +463,7 @@ gvc_mixer_ui_device_get_best_profile (GvcMixerUIDevice *device,
 {
         GList *candidates, *l;
         const gchar *result;
-        gchar *skip_prefix;
+        const gchar *skip_prefix;
         gchar *canonical_name_selected;
 
         if (device->priv->type == UIDeviceInput)
@@ -505,7 +505,7 @@ gvc_mixer_ui_device_get_best_profile (GvcMixerUIDevice *device,
         /* 2) Try to keep the other side unchanged if possible */
         if (result == NULL) {
                 guint prio = 0;
-                gchar *skip_prefix_reverse = device->priv->type == UIDeviceInput ? "input:" : "output:";
+                const gchar *skip_prefix_reverse = device->priv->type == UIDeviceInput ? "input:" : "output:";
                 gchar *current_reverse = get_profile_canonical_name (current, skip_prefix_reverse);
                 for (l = candidates; l != NULL; l = l->next) {
                         gchar *p_reverse;