diff --git a/gas/ChangeLog b/gas/ChangeLog
index 5a391a22636..f6b357709b2 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,9 @@
+2022-08-05  Nick Clifton  <nickc@redhat.com>
+
+	PR 29447
+	* read.c (read_symbol_name): Pass 0 as the length parameter when
+	invoking mbstowc in order to check the validity of a wide string.
+
 2022-07-18  Claudiu Zissulescu  <claziss@synopsys.com>
 
 	* config/tc-arc.c (md_assembly): Update strspn string with the
diff --git a/gas/read.c b/gas/read.c
index 800712466be..e23be666dde 100644
--- a/gas/read.c
+++ b/gas/read.c
@@ -1629,7 +1629,10 @@ read_symbol_name (void)
       /* Since quoted symbol names can contain non-ASCII characters,
 	 check the string and warn if it cannot be recognised by the
 	 current character set.  */
-      if (mbstowcs (NULL, name, len) == (size_t) -1)
+      /* PR 29447: mbstowcs ignores the third (length) parameter when
+	 the first (destination) parameter is NULL.  For clarity sake
+	 therefore we pass 0 rather than 'len' as the third parameter.  */
+      if (mbstowcs (NULL, name, 0) == (size_t) -1)
 	as_warn (_("symbol name not recognised in the current locale"));
     }
   else if (is_name_beginner (c) || (input_from_string && c == FAKE_LABEL_CHAR))