diff --git a/src/fmt/format.go b/src/fmt/format.go
index 91103f2c07..94c9b71e7a 100644
--- a/src/fmt/format.go
+++ b/src/fmt/format.go
@@ -57,6 +57,8 @@ func (f *fmt) clearflags() {
 
 func (f *fmt) init(buf *buffer) {
 	f.buf = buf
+	f.wid = 0
+	f.prec = 0
 	f.clearflags()
 }