diff --git a/src/core/message_queue.cpp b/src/core/message_queue.cpp
index 0b0d934..502d89a 100644
--- a/src/core/message_queue.cpp
+++ b/src/core/message_queue.cpp
@@ -101,7 +101,7 @@ void message_queue::run(bot::settings::settings *settings, submit_queue *submit_
         if (!m_queue.empty()) {
             const message message = m_queue.front();
             m_queue.pop();
-            for (message_queue_size_callback &callback : m_callbacks)
+            for (const message_queue_size_callback &callback : m_callbacks)
                 callback(m_queue.size());
             m_mutex.unlock();
 
diff --git a/src/core/submit_queue.cpp b/src/core/submit_queue.cpp
index 58a98aa..74962e9 100644
--- a/src/core/submit_queue.cpp
+++ b/src/core/submit_queue.cpp
@@ -42,7 +42,7 @@ void submit_queue::run(dpp::cluster *bot)
         if (!m_queue.empty()) {
             const translated_message message = m_queue.front();
             m_queue.pop();
-            for (submit_queue_size_callback &callback : m_callbacks)
+            for (const submit_queue_size_callback &callback : m_callbacks)
                 callback(m_queue.size());
             m_mutex.unlock();