diff --git a/src/string_util.cpp b/src/string_util.cpp
index 9159850..0b75a45 100644
--- a/src/string_util.cpp
+++ b/src/string_util.cpp
@@ -105,15 +105,13 @@ std::string lower(std::string s)
     return s;
 }
 
-std::string trim_left(const std::string &s, const char *t /* = SPACES */)
+std::string trim_left(std::string d, const char *t /* = SPACES */)
 {
-    std::string d(s);
-    return d.erase(0, s.find_first_not_of(t));
+    return d.erase(0, d.find_first_not_of(t));
 }
 
-std::string trim_right(const std::string &s, const char *t /* = SPACES */)
+std::string trim_right(std::string d, const char *t /* = SPACES */)
 {
-    std::string d(s);
     std::string::size_type i(d.find_last_not_of(t));
     if(i == std::string::npos){
         return "";
@@ -122,9 +120,9 @@ std::string trim_right(const std::string &s, const char *t /* = SPACES */)
     }
 }
 
-std::string trim(const std::string &s, const char *t /* = SPACES */)
+std::string trim(std::string s, const char *t /* = SPACES */)
 {
-    return trim_left(trim_right(s, t), t);
+    return trim_left(trim_right(std::move(s), t), t);
 }
 
 //
diff --git a/src/string_util.h b/src/string_util.h
index 3ac71ff..9132afe 100644
--- a/src/string_util.h
+++ b/src/string_util.h
@@ -75,9 +75,9 @@ off_t cvt_strtoofft(const char* str, int base);
 //
 // String Manipulation
 //
-std::string trim_left(const std::string &s, const char *t = SPACES);
-std::string trim_right(const std::string &s, const char *t = SPACES);
-std::string trim(const std::string &s, const char *t = SPACES);
+std::string trim_left(std::string s, const char *t = SPACES);
+std::string trim_right(std::string s, const char *t = SPACES);
+std::string trim(std::string s, const char *t = SPACES);
 std::string lower(std::string s);
 
 //