diff --git a/historic/jam/src/builtins.h b/historic/jam/src/builtins.h
index 51cd7beb2..c405797f1 100644
--- a/historic/jam/src/builtins.h
+++ b/historic/jam/src/builtins.h
@@ -34,4 +34,6 @@ LIST *builtin_pwd( PARSE *parse, FRAME *args );
 LIST *builtin_update( PARSE *parse, FRAME *args );
 LIST *builtin_search_for_target( PARSE *parse, FRAME *args );
 
+void backtrace( FRAME *frame );
+
 #endif
diff --git a/jam_src/builtins.h b/jam_src/builtins.h
index 51cd7beb2..c405797f1 100644
--- a/jam_src/builtins.h
+++ b/jam_src/builtins.h
@@ -34,4 +34,6 @@ LIST *builtin_pwd( PARSE *parse, FRAME *args );
 LIST *builtin_update( PARSE *parse, FRAME *args );
 LIST *builtin_search_for_target( PARSE *parse, FRAME *args );
 
+void backtrace( FRAME *frame );
+
 #endif