Anyway, here's the patch:

Index: libguile/ports.h
===================================================================
RCS file: /egcs/carton/cvsfiles/guile/guile-core/libguile/ports.h,v
retrieving revision 1.33
retrieving revision 1.34
diff -u -r1.33 -r1.34
--- libguile/ports.h	1998/10/30 08:22:50	1.33
+++ libguile/ports.h	1998/11/05 16:02:55	1.34
@@ -93,7 +93,7 @@
 #define SCM_CRDY	(32L<<16) /* Should char-ready? return #t? */
 
 /* A mask used to clear the char-ready port flag. */
-#define SCM_CUC		0x001fffffL
+#define SCM_CUC		(~SCM_CRDY)
 
 #define SCM_PORTP(x) (SCM_TYP7(x)==scm_tc7_port)
 #define SCM_OPPORTP(x) (((0x7f | SCM_OPN) & SCM_CAR(x))==(scm_tc7_port | SCM_OPN))