diff --git a/src/util/string-helper.cpp b/src/util/string-helper.cpp
index 44083b3..4a4808f 100644
--- a/src/util/string-helper.cpp
+++ b/src/util/string-helper.cpp
@@ -20,14 +20,13 @@
  */
 
 #include "string-helper.hpp"
+#include "../encoding/buffer.hpp"
 #include "../encoding/buffer-stream.hpp"
 #include "../security/transform/buffer-source.hpp"
 #include "../security/transform/hex-decode.hpp"
 #include "../security/transform/hex-encode.hpp"
 #include "../security/transform/stream-sink.hpp"
 
-#include <boost/algorithm/string/trim.hpp>
-
 #include <sstream>
 #include <iomanip>
 
@@ -109,24 +108,6 @@
   return os.buf();
 }
 
-void
-trimLeft(std::string& str)
-{
-  boost::algorithm::trim_left(str);
-}
-
-void
-trimRight(std::string& str)
-{
-  boost::algorithm::trim_right(str);
-}
-
-void
-trim(std::string& str)
-{
-  boost::algorithm::trim(str);
-}
-
 std::string
 unescape(const std::string& str)
 {
diff --git a/src/util/string-helper.hpp b/src/util/string-helper.hpp
index 7785f69..3f1a303 100644
--- a/src/util/string-helper.hpp
+++ b/src/util/string-helper.hpp
@@ -23,10 +23,11 @@
 #define NDN_UTIL_STRING_HELPER_HPP
 
 #include "../common.hpp"
-#include "../encoding/buffer.hpp"
 
 namespace ndn {
 
+class Buffer;
+
 class StringHelperError : public std::invalid_argument
 {
 public:
@@ -111,24 +112,6 @@
 fromHex(const std::string& hexString);
 
 /**
- * @brief Modify str in place to erase whitespace on the left
- */
-void
-trimLeft(std::string& str);
-
-/**
- * @brief Modify str in place to erase whitespace on the right
- */
-void
-trimRight(std::string& str);
-
-/**
- * @brief Modify str in place to erase whitespace on the left and right
- */
-void
-trim(std::string& str);
-
-/**
  * @brief Decode a percent-encoded string
  * @see RFC 3986 section 2
  *