diff --git a/http2/hpack/varint/hpack_varint_encoder_test.cc b/http2/hpack/varint/hpack_varint_encoder_test.cc
index 94f9a9e..23c19c4 100644
--- a/http2/hpack/varint/hpack_varint_encoder_test.cc
+++ b/http2/hpack/varint/hpack_varint_encoder_test.cc
@@ -31,7 +31,7 @@
 // Encode integers that fit in the prefix.
 TEST(HpackVarintEncoderTest, Short) {
   for (size_t i = 0; i < HTTP2_ARRAYSIZE(kShortTestData); ++i) {
-    Http2String output;
+    std::string output;
     HpackVarintEncoder::Encode(kShortTestData[i].high_bits,
                                kShortTestData[i].prefix_length,
                                kShortTestData[i].value, &output);
@@ -104,10 +104,10 @@
   // Test encoding byte by byte, also test encoding in
   // a single ResumeEncoding() call.
     for (size_t i = 0; i < HTTP2_ARRAYSIZE(kLongTestData); ++i) {
-      Http2String expected_encoding =
+      std::string expected_encoding =
           Http2HexDecode(kLongTestData[i].expected_encoding);
 
-      Http2String output;
+      std::string output;
       HpackVarintEncoder::Encode(kLongTestData[i].high_bits,
                                  kLongTestData[i].prefix_length,
                                  kLongTestData[i].value, &output);
@@ -131,7 +131,7 @@
 // happens exactly when encoding  the value 2^prefix_length - 1.
 TEST(HpackVarintEncoderTest, LastByteIsZero) {
   for (size_t i = 0; i < HTTP2_ARRAYSIZE(kLastByteIsZeroTestData); ++i) {
-    Http2String output;
+    std::string output;
     HpackVarintEncoder::Encode(kLastByteIsZeroTestData[i].high_bits,
                                kLastByteIsZeroTestData[i].prefix_length,
                                kLastByteIsZeroTestData[i].value, &output);
@@ -144,7 +144,7 @@
 
 // Test that encoder appends correctly to non-empty string.
 TEST(HpackVarintEncoderTest, Append) {
-  Http2String output("foo");
+  std::string output("foo");
   EXPECT_EQ(Http2HexDecode("666f6f"), output);
 
   HpackVarintEncoder::Encode(0b10011000, 3, 103, &output);