diff --git a/libguile/gc_os_dep.c b/libguile/gc_os_dep.c
index 51d27b1ad..dcd5a3152 100644
--- a/libguile/gc_os_dep.c
+++ b/libguile/gc_os_dep.c
@@ -374,6 +374,11 @@ typedef int GC_bool;
 #    define GNU
 #    define mach_type_known
 # endif
+# if defined(__SCO_VERSION__)
+#    define I386
+#    define SYSV
+#    define mach_type_known
+# endif
 
 /* Feel free to add more clauses here */