diff --git a/libguile/scmconfig.h.in b/libguile/scmconfig.h.in
index 2322c7d21..1404c607a 100644
--- a/libguile/scmconfig.h.in
+++ b/libguile/scmconfig.h.in
@@ -164,6 +164,9 @@
 /* Define if the operating system supplies bzero without declaring it. */
 #undef MISSING_BZERO_DECL
 
+/* Define if the operating system supplies sleep without declaring it. */
+#undef MISSING_SLEEP_DECL
+
 /* Define if the operating system supplies usleep without declaring it. */
 #undef MISSING_USLEEP_DECL