1 files changed, 5 insertions, 3 deletions

diff --git a/src/syntax.c b/src/syntax.c
index d45936b2b28..30560affdf0 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -1333,9 +1333,11 @@ DEFUN ("internal-describe-syntax-value", Finternal_describe_syntax_value,
     insert_string (" (nestable)");
 
   if (prefix)
-    insert1 (Fsubstitute_command_keys
-             (build_string
-              (",\n\t  is a prefix character for `backward-prefix-chars'")));
+    {
+      AUTO_STRING (prefixdoc,
+                   ",\n\t  is a prefix character for `backward-prefix-chars'");
+      insert1 (Fsubstitute_command_keys (prefixdoc));
+    }
 
   return syntax;
 }