diff --git a/dep/sl.h b/dep/sl.h
index 4a55c70..42f49c1 100644
--- a/dep/sl.h
+++ b/dep/sl.h
@@ -4,6 +4,7 @@
 // define SL_IMPL before including this file in a source file
 #ifndef SL_SINGLEFILE_H
 #define SL_SINGLEFILE_H
+#define SL_IMPL_NO_INCLUDE
 #line 1 "sl.h"
 #ifndef SL_H
 #define SL_H
@@ -46,7 +47,6 @@ long slcount(const slist_t *sl);
 #ifdef SL_IMPL
 #ifndef SL_IMPL_ONCE
 #define SL_IMPL_ONCE
-#define SL_IMPL_NO_INCLUDE
 #line 1 "sl.c"
 #ifndef SL_IMPL_NO_INCLUDE
 #include "sl.h"