Allow prec==0.
diff --git a/src/lib9/encodefmt.c b/src/lib9/encodefmt.c
index 9a5cbfc..5dd2f48 100644
--- a/src/lib9/encodefmt.c
+++ b/src/lib9/encodefmt.c
@@ -11,7 +11,7 @@
 	uchar *b;
 	char obuf[64];	// rsc optimization
 
-	if(!(f->flags&FmtPrec) || f->prec < 1)
+	if(!(f->flags&FmtPrec) || f->prec < 0)
 		goto error;
 
 	b = va_arg(f->args, uchar*);