--- gcal-3.6/lib/spawn.in.h  2010-03-22 13:31:49.000000000 +0100
+++ gcal-3.6a/lib/spawn.in.h 2010-10-30 16:57:51.000000000 +0200
@@ -24,6 +24,11 @@
 /* The include_next requires a split double-inclusion guard.  */
 #if @HAVE_SPAWN_H@
 # @INCLUDE_NEXT@ @NEXT_SPAWN_H@
+#else
+/* At least the sched.h and the signal.h are required
+   from gcal or glibc  */
+#include <sched.h>
+#include <signal.h>
 #endif
 
 #ifndef _GL_SPAWN_H