diff --git a/src/network/compressor.cc b/src/network/compressor.cc
index 9f9500f..37c95c5 100644
--- a/src/network/compressor.cc
+++ b/src/network/compressor.cc
@@ -6,7 +6,7 @@
 using namespace Network;
 using namespace std;
 
-string Compressor::compress_str( const string input )
+string Compressor::compress_str( const string &input )
 {
   long unsigned int len = BUFFER_SIZE;
   dos_assert( Z_OK == compress( buffer, &len,
@@ -15,7 +15,7 @@ string Compressor::compress_str( const string input )
   return string( reinterpret_cast<char *>( buffer ), len );
 }
 
-string Compressor::uncompress_str( const string input )
+string Compressor::uncompress_str( const string &input )
 {
   long unsigned int len = BUFFER_SIZE;
   dos_assert( Z_OK == uncompress( buffer, &len,
diff --git a/src/network/compressor.h b/src/network/compressor.h
index 0d66bc7..ffeca99 100644
--- a/src/network/compressor.h
+++ b/src/network/compressor.h
@@ -14,8 +14,8 @@ namespace Network {
     Compressor() : buffer( NULL ) { buffer = new unsigned char[ BUFFER_SIZE ]; }
     ~Compressor() { if ( buffer ) { delete[] buffer; } }
 
-    std::string compress_str( const std::string input );
-    std::string uncompress_str( const std::string input );
+    std::string compress_str( const std::string &input );
+    std::string uncompress_str( const std::string &input );
 
     /* unused */
     Compressor( const Compressor & );