diff --git a/decode.go b/decode.go
index 20494cc0..49e5b998 100644
--- a/decode.go
+++ b/decode.go
@@ -47,6 +47,7 @@ func PutDecoder(dec *Decoder) {
 	dec.r = nil
 	dec.s = nil
 	dec.bsr.data = nil
+	dec.flags = 0
 	// Keep buf capacity for reuse, but drop oversized buffers to prevent
 	// the pool from retaining memory from large decode operations.
 	if poolBufOversized(cap(dec.buf)) {
diff --git a/encode.go b/encode.go
index 0e87555c..8d484ca5 100644
--- a/encode.go
+++ b/encode.go
@@ -54,6 +54,7 @@ func GetEncoder() *Encoder {
 
 func PutEncoder(enc *Encoder) {
 	enc.w = nil
+	enc.flags = 0
 	// Keep wbuf capacity for reuse, but drop oversized buffers.
 	if poolBufOversized(cap(enc.wbuf)) {
 		enc.wbuf = nil
diff --git a/pool_test.go b/pool_test.go
index 802b2960..1aa12f3c 100644
--- a/pool_test.go
+++ b/pool_test.go
@@ -78,6 +78,28 @@ func TestPoolBufferLimitDecoder(t *testing.T) {
 	PutDecoder(dec)
 }
 
+func TestPutEncoderClearsFlags(t *testing.T) {
+	enc := GetEncoder()
+	enc.UseCompactInts(true)
+	enc.SetSortMapKeys(true)
+	PutEncoder(enc)
+
+	if enc.flags != 0 {
+		t.Fatalf("encoder flags=%d after PutEncoder, want 0", enc.flags)
+	}
+}
+
+func TestPutDecoderClearsFlags(t *testing.T) {
+	dec := GetDecoder()
+	dec.UseInternedStrings(true)
+	dec.DisallowUnknownFields(true)
+	PutDecoder(dec)
+
+	if dec.flags != 0 {
+		t.Fatalf("decoder flags=%d after PutDecoder, want 0", dec.flags)
+	}
+}
+
 func TestSetPoolBufferLimitClamp(t *testing.T) {
 	SetPoolBufferLimit(-1)
 	if got := getPoolBufferLimit(); got != defaultPoolBufferLimit {