diff --git a/include/chibi/features.h b/include/chibi/features.h
index 4eb8734c..a5cda9c6 100644
--- a/include/chibi/features.h
+++ b/include/chibi/features.h
@@ -436,7 +436,7 @@
 #define SEXP_USE_FLAT_SYNTACTIC_CLOSURES 0
 #endif
 
-#if SEXP_USE_UNWRAPPED_TOPLEVEL_BINDINGS
+#ifndef SEXP_USE_UNWRAPPED_TOPLEVEL_BINDINGS
 #define SEXP_USE_UNWRAPPED_TOPLEVEL_BINDINGS 0
 #endif