diff --git a/src/alloc.c b/src/alloc.c
index f0c77a26710..4d44134e1cd 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4659,7 +4659,7 @@ void
 check_pure_size ()
 {
   if (pure_bytes_used_before_overflow)
-    message ("Pure Lisp storage overflow (approx. %d bytes needed)",
+    message ("emacs:0:Pure Lisp storage overflow (approx. %d bytes needed)",
 	     (int) (pure_bytes_used + pure_bytes_used_before_overflow));
 }