diff --git a/libguile/num2integral.i.c b/libguile/num2integral.i.c
index a9bd5c718..065dc1936 100644
--- a/libguile/num2integral.i.c
+++ b/libguile/num2integral.i.c
@@ -1,5 +1,9 @@
 /* this file is #include'd (many times) by numbers.c */
 
+#if HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
 #ifndef UNSIGNED_ITYPE
 #ifdef UNSIGNED
 #define UNSIGNED_ITYPE ITYPE