diff --git a/include/tools/regexTools.h b/include/tools/regexTools.h
index f5656eedd..ef7a3a52b 100644
--- a/include/tools/regexTools.h
+++ b/include/tools/regexTools.h
@@ -27,7 +27,7 @@ std::string replaceRegex(const std::string& content,
                          const std::string& replacement,
                          const std::string& regex);
 std::string appendToFirstOccurence(const std::string& content,
-                                   const std::string regex,
+                                   const std::string& regex,
                                    const std::string& replacement);
 
 #endif
diff --git a/src/tools/regexTools.cpp b/src/tools/regexTools.cpp
index c31ffd525..3f1d5b8ab 100644
--- a/src/tools/regexTools.cpp
+++ b/src/tools/regexTools.cpp
@@ -76,7 +76,7 @@ std::string replaceRegex(const std::string& content,
 }
 
 std::string appendToFirstOccurence(const std::string& content,
-                                   const std::string regex,
+                                   const std::string& regex,
                                    const std::string& replacement)
 {
   ucnv_setDefaultName("UTF-8");