diff --git a/args.go b/args.go
index 938e62e..a2290a8 100644
--- a/args.go
+++ b/args.go
@@ -644,11 +644,3 @@ func peekAllArgBytesToDst(dst [][]byte, h []argsKV, k []byte) [][]byte {
 	}
 	return dst
 }
-
-func peekArgsKeys(dst [][]byte, h []argsKV) [][]byte {
-	for i, n := 0, len(h); i < n; i++ {
-		kv := &h[i]
-		dst = append(dst, kv.key)
-	}
-	return dst
-}
diff --git a/header.go b/header.go
index b6f9a8f..9971bb5 100644
--- a/header.go
+++ b/header.go
@@ -1992,9 +1992,25 @@ func (h *ResponseHeader) peekAll(key []byte) [][]byte {
 // either though ReleaseRequest or your request handler returning.
 // Any future calls to the Peek* will modify the returned value.
 // Do not store references to returned value. Make copies instead.
-func (h *header) PeekKeys() [][]byte {
+func (h *RequestHeader) PeekKeys() [][]byte {
 	h.mulHeader = h.mulHeader[:0]
-	h.mulHeader = peekArgsKeys(h.mulHeader, h.h)
+	for key := range h.All() {
+		h.mulHeader = append(h.mulHeader, key)
+	}
+	return h.mulHeader
+}
+
+// PeekKeys return all header keys.
+//
+// The returned value is valid until the request is released,
+// either though ReleaseRequest or your request handler returning.
+// Any future calls to the Peek* will modify the returned value.
+// Do not store references to returned value. Make copies instead.
+func (h *ResponseHeader) PeekKeys() [][]byte {
+	h.mulHeader = h.mulHeader[:0]
+	for key := range h.All() {
+		h.mulHeader = append(h.mulHeader, key)
+	}
 	return h.mulHeader
 }
 
diff --git a/header_test.go b/header_test.go
index 430f292..da0b75e 100644
--- a/header_test.go
+++ b/header_test.go
@@ -3426,13 +3426,13 @@ func TestRequestHeader_Keys(t *testing.T) {
 		t.Fatal(err)
 	}
 	actualKeys := h.PeekKeys()
-	expectedKeys := [][]byte{s2b("keep-alive"), s2b("aaa")}
-	if reflect.DeepEqual(actualKeys, expectedKeys) {
+	expectedKeys := [][]byte{[]byte("Content-Type"), []byte("Trailer"), []byte("Connection")}
+	if !reflect.DeepEqual(actualKeys, expectedKeys) {
 		t.Fatalf("Unexpected value %q. Expected %q", actualKeys, expectedKeys)
 	}
 	actualTrailerKeys := h.PeekTrailerKeys()
-	expectedTrailerKeys := [][]byte{s2b("aaa"), s2b("bbb"), s2b("ccc")}
-	if reflect.DeepEqual(actualTrailerKeys, expectedTrailerKeys) {
+	expectedTrailerKeys := [][]byte{s2b("Aaa"), s2b("Bbb"), s2b("Ccc")}
+	if !reflect.DeepEqual(actualTrailerKeys, expectedTrailerKeys) {
 		t.Fatalf("Unexpected value %q. Expected %q", actualTrailerKeys, expectedTrailerKeys)
 	}
 }
@@ -3446,13 +3446,13 @@ func TestResponseHeader_Keys(t *testing.T) {
 		t.Fatal(err)
 	}
 	actualKeys := h.PeekKeys()
-	expectedKeys := [][]byte{s2b("keep-alive"), s2b("aaa")}
-	if reflect.DeepEqual(actualKeys, expectedKeys) {
+	expectedKeys := [][]byte{[]byte("Content-Type"), []byte("Trailer"), []byte("Connection")}
+	if !reflect.DeepEqual(actualKeys, expectedKeys) {
 		t.Fatalf("Unexpected value %q. Expected %q", actualKeys, expectedKeys)
 	}
 	actualTrailerKeys := h.PeekTrailerKeys()
-	expectedTrailerKeys := [][]byte{s2b("aaa"), s2b("bbb"), s2b("ccc")}
-	if reflect.DeepEqual(actualTrailerKeys, expectedTrailerKeys) {
+	expectedTrailerKeys := [][]byte{s2b("Aaa"), s2b("Bbb"), s2b("Ccc")}
+	if !reflect.DeepEqual(actualTrailerKeys, expectedTrailerKeys) {
 		t.Fatalf("Unexpected value %q. Expected %q", actualTrailerKeys, expectedTrailerKeys)
 	}
 }