diff --git a/src/c/symbols_list.h b/src/c/symbols_list.h
index 1f8e89184..e0d0ba387 100644
--- a/src/c/symbols_list.h
+++ b/src/c/symbols_list.h
@@ -1057,7 +1057,7 @@ cl_symbols[] = {
 {SYS_ "FILL-POINTER-SET", SI_ORDINARY, si_fill_pointer_set, 2, OBJNULL},
 {SYS_ "FIXNUMP", SI_ORDINARY, si_fixnump, 1, OBJNULL},
 {SYS_ "FORMAT-ERROR", SI_ORDINARY, NULL, -1, OBJNULL},
-#ifndef ECL_CMU_FORMAT
+#ifdef ECL_CMU_FORMAT
 {SYS_ "FORMATTER-AUX", SI_ORDINARY, NULL, -1, OBJNULL},
 #else
 {SYS_ "FORMATTER-AUX", SI_ORDINARY, si_formatter_aux, -1, OBJNULL},