diff --git a/sys/src/9/pc/acpi.c b/sys/src/9/pc/acpi.c
index f50ad8c01..51b34adda 100644
--- a/sys/src/9/pc/acpi.c
+++ b/sys/src/9/pc/acpi.c
@@ -146,7 +146,7 @@ maptable(uvlong xpa)
 
 	tbltab[ntbltab++] = t = a;
 
-	if(0) print("acpi: %llux %.4s %d\n", xpa, t->sig, l);
+	if(0) print("acpi: %llux %.4s %d\n", xpa, (char*)t->sig, l);
 
 	p = (uchar*)t;
 	e = p + l;