Index: vesa.c
===================================================================
--- vesa.c	(revision 293386)
+++ vesa.c	(working copy)
@@ -819,6 +819,11 @@
 	regs.R_AX = 0x4f00;
 
 	vmbuf = x86bios_alloc(&offs, sizeof(*buf), M_WAITOK);
+	if (vmbuf == NULL) {
+		printf("%s: x86bios_alloc failed!\n", __func__);
+		DTRACE_PROBE1(x86bios_alloc_failed, int, vmbuf);
+		goto fail;
+	}
 
 	regs.R_ES = X86BIOS_PHYSTOSEG(offs);
 	regs.R_DI = X86BIOS_PHYSTOOFF(offs);