diff --git a/src/utils/system.cc b/src/utils/system.cc
index 937bbb01..60f3cdc6 100644
--- a/src/utils/system.cc
+++ b/src/utils/system.cc
@@ -65,13 +65,13 @@ std::list<std::string> expandEnv(const std::string& var, int flags) {
     return vars;
 }
 
-bool createDir(std::string dir, int mode, std::string *error) {
+bool createDir(const std::string& dir, int mode, std::string *error) {
 
     return true;
 }
 
 
-bool isFile(std::string f) {
+bool isFile(const std::string& f) {
 
     return true;
 }
diff --git a/src/utils/system.h b/src/utils/system.h
index 674fab18..b3033b44 100644
--- a/src/utils/system.h
+++ b/src/utils/system.h
@@ -33,8 +33,8 @@ std::string find_resource(const std::string& file, const std::string& config,
     std::string *err);
 std::string get_path(const std::string& file);
 std::list<std::string> expandEnv(const std::string& var, int flags);
-bool createDir(std::string dir, int mode, std::string *error);
-bool isFile(std::string f);
+bool createDir(const std::string& dir, int mode, std::string *error);
+bool isFile(const std::string& f);
 
 }  // namespace utils
 }  // namespace modsecurity
diff --git a/test/cppcheck_suppressions.txt b/test/cppcheck_suppressions.txt
index 7563c112..ca662a85 100644
--- a/test/cppcheck_suppressions.txt
+++ b/test/cppcheck_suppressions.txt
@@ -62,8 +62,6 @@ ctunullpointer:src/rule_with_operator.cc:95
 passedByValue:src/variables/global.h:109
 passedByValue:src/variables/global.h:110
 passedByValue:src/parser/driver.cc:45
-passedByValue:src/utils/system.cc:154
-passedByValue:src/utils/system.cc:166
 passedByValue:test/common/modsecurity_test.cc:49
 passedByValue:test/common/modsecurity_test.cc:98