diff --git a/src/mu-msg-str.c b/src/mu-msg-str.c
index bdec687d..16872085 100644
--- a/src/mu-msg-str.c
+++ b/src/mu-msg-str.c
@@ -44,7 +44,10 @@ mu_msg_str_date (time_t t)
 const char*
 mu_msg_str_size_s  (size_t s)
 {
+	/* note: we we use the powers-of-10, not powers-of-2 */
+
 	static char buf[32];
+	
 	if (s >= 1000 * 1000)
 		g_snprintf(buf, 32, "%.1fM", (double)s/(1000*1000));
 	else
diff --git a/src/mu-msg-str.h b/src/mu-msg-str.h
index a3454daf..ac6093eb 100644
--- a/src/mu-msg-str.h
+++ b/src/mu-msg-str.h
@@ -41,7 +41,7 @@
  * for what to do with it
  */
 const char* mu_msg_str_date_s (time_t t) G_GNUC_CONST;
-char*       mu_msg_str_date   (time_t t);
+char*       mu_msg_str_date   (time_t t) G_GNUC_WARN_UNUSED_RESULT;
 
 
 /** 
@@ -58,7 +58,7 @@ char*       mu_msg_str_date   (time_t t);
  * for what to do with it
  */
 const char* mu_msg_str_size_s  (size_t s) G_GNUC_CONST;
-char*       mu_msg_str_size    (size_t s);
+char*       mu_msg_str_size    (size_t s) G_GNUC_WARN_UNUSED_RESULT;
 
 /** 
  * get a display string for a given set of flags, OR'ed in 
@@ -76,7 +76,7 @@ char*       mu_msg_str_size    (size_t s);
  * for what to do with it
  */
 const char* mu_msg_str_flags_s  (MuMsgFlags flags) G_GNUC_CONST;
-char*       mu_msg_str_flags    (MuMsgFlags flags);
+char*       mu_msg_str_flags    (MuMsgFlags flags) G_GNUC_WARN_UNUSED_RESULT;
 
 
 /**