--- src/sys/vfs/specfs/spec_vnops.c	2007/07/20 17:21:53	1.52
+++ src/sys/vfs/specfs/spec_vnops.c	2007/07/23 19:19:11	1.53
@@ -47,6 +47,7 @@
 #include <sys/stat.h>
 #include <sys/fcntl.h>
 #include <sys/vmmeter.h>
+#include <sys/bus.h>
 #include <sys/tty.h>
 
 #include <vm/vm.h>
@@ -494,7 +495,10 @@ spec_strategy(struct vop_strategy_args *
          * Device iosize limitations only apply to read and write.  Shortcut
          * the I/O if it fits.
          */
-	maxiosize = vp->v_rdev->si_iosize_max;
+	if ((maxiosize = vp->v_rdev->si_iosize_max) == 0) {
+		kprintf("%s: si_iosize_max not set!\n", dev_dname(vp->v_rdev));
+		maxiosize = MAXPHYS;
+	}
 #if SPEC_CHAIN_DEBUG & 2
 	maxiosize = 4096;
 #endif