diff --git a/common/strings.cpp b/common/strings.cpp
index 29bef8993..a4ea9f3da 100644
--- a/common/strings.cpp
+++ b/common/strings.cpp
@@ -961,14 +961,14 @@ bool Strings::IsValidJson(const std::string &json)
 	return result;
 }
 
-std::string Strings::Implode(const std::string& glue, std::unordered_set<std::string> src)
+std::string Strings::Implode(const std::string& glue, const std::unordered_set<std::string>& src)
 {
 	if (src.empty()) {
 		return {};
 	}
 
-	std::ostringstream                        output;
-	std::unordered_set<std::string>::iterator src_iter;
+	std::ostringstream                              output;
+	std::unordered_set<std::string>::const_iterator src_iter;
 
 	for (src_iter = src.begin(); src_iter != src.end(); src_iter++) {
 		output << *src_iter << glue;
diff --git a/common/strings.h b/common/strings.h
index ab2e71011..ef7d93440 100644
--- a/common/strings.h
+++ b/common/strings.h
@@ -77,7 +77,7 @@ public:
 	static std::string Escape(const std::string &s);
 	static std::string GetBetween(const std::string &s, std::string start_delim, std::string stop_delim);
 	static std::string Implode(const std::string& glue, std::vector<std::string> src);
-	static std::string Implode(const std::string& glue, std::unordered_set<std::string> src);
+	static std::string Implode(const std::string& glue, const std::unordered_set<std::string>& src);
 	static std::string Join(const std::vector<std::string> &ar, const std::string &delim);
 	static std::string Join(const std::vector<uint32_t> &ar, const std::string &delim);
 	static std::string MillisecondsToTime(int duration);