diff --git a/zapio/writer.go b/zapio/writer.go
index 29699c86d..8b2911564 100644
--- a/zapio/writer.go
+++ b/zapio/writer.go
@@ -23,6 +23,7 @@ package zapio
 import (
 	"bytes"
 	"io"
+	"unsafe"
 
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
@@ -114,7 +115,10 @@ func (w *Writer) flush(allowEmpty bool) {
 }
 
 func (w *Writer) log(b []byte) {
-	if ce := w.Log.Check(w.Level, string(b)); ce != nil {
+	// This is unsafe, but the contract is that a CheckedEntry is no longer
+	// valid once we call ce.Write, so it promises not to reuse this
+	// string.
+	if ce := w.Log.Check(w.Level, *(*string)(unsafe.Pointer(&b))); ce != nil {
 		ce.Write()
 	}
 }