diff --git a/backends/hash_hashlib/hlib_sha256.cpp b/backends/hash_hashlib/hlib_sha256.cpp
index 4b8c07d..52bf413 100644
--- a/backends/hash_hashlib/hlib_sha256.cpp
+++ b/backends/hash_hashlib/hlib_sha256.cpp
@@ -1,10 +1,10 @@
 #include "hlib_sha256.h"
 
-std::string HashLibSHA256::compute(const void *data, size_t num_bytes) {
+String HashLibSHA256::compute(const void *data, size_t num_bytes) {
 	return hasher.operator()(data, num_bytes);
 }
 
-std::string HashLibSHA256::compute(const std::string &text) {
+String HashLibSHA256::compute(const String &text) {
 	return hasher.operator()(text);
 }
 
@@ -12,7 +12,7 @@ void HashLibSHA256::add(const void *data, size_t num_bytes) {
 	hasher.add(data, num_bytes);
 }
 
-std::string HashLibSHA256::get_hash() {
+String HashLibSHA256::get_hash() {
 	return hasher.getHash();
 }
 
diff --git a/backends/hash_hashlib/hlib_sha256.h b/backends/hash_hashlib/hlib_sha256.h
index e07b211..a1aafa4 100644
--- a/backends/hash_hashlib/hlib_sha256.h
+++ b/backends/hash_hashlib/hlib_sha256.h
@@ -7,11 +7,11 @@
 
 class HashLibSHA256 : public SHA256 {
 public:
-	std::string compute(const void *data, size_t num_bytes);
-	std::string compute(const std::string &text);
+	String compute(const void *data, size_t num_bytes);
+	String compute(const String &text);
 
 	void add(const void *data, size_t num_bytes);
-	std::string get_hash();
+	String get_hash();
 	void get_hash(unsigned char *buffer, size_t buffer_len);
 
 	void reset();
diff --git a/core/hash/sha256.h b/core/hash/sha256.h
index 9f96eff..c609817 100644
--- a/core/hash/sha256.h
+++ b/core/hash/sha256.h
@@ -1,7 +1,7 @@
 #ifndef SHA256_H
 #define SHA256_H
 
-#include <string>
+#include "core/string.h"
 
 #include "core/reference.h"
 
@@ -9,11 +9,11 @@ class SHA256 : public Reference {
 	RCPP_OBJECT(SHA256, Reference);
 
 public:
-	virtual std::string compute(const void *data, size_t num_bytes) = 0;
-	virtual std::string compute(const std::string &text) = 0;
+	virtual String compute(const void *data, size_t num_bytes) = 0;
+	virtual String compute(const String &text) = 0;
 
 	virtual void add(const void *data, size_t num_bytes) = 0;
-	virtual std::string get_hash() = 0;
+	virtual String get_hash() = 0;
 	virtual void get_hash(unsigned char *buffer, size_t buffer_len) = 0;
 
 	virtual void reset() = 0;