diff --git a/base/commands_queue.cpp b/base/commands_queue.cpp
index f9fb724c51..881c41cc50 100644
--- a/base/commands_queue.cpp
+++ b/base/commands_queue.cpp
@@ -9,11 +9,11 @@
 
 namespace core
 {
-  CommandsQueue::Environment::Environment(int threadNum)
+  CommandsQueue::Environment::Environment(size_t threadNum)
     : m_threadNum(threadNum)
   {}
 
-  int CommandsQueue::Environment::threadNum() const
+  size_t CommandsQueue::Environment::threadNum() const
   {
     return m_threadNum;
   }
@@ -69,7 +69,7 @@ namespace core
     finish();
   }
 
-  CommandsQueue::Routine::Routine(CommandsQueue * parent, int idx)
+  CommandsQueue::Routine::Routine(CommandsQueue * parent, size_t idx)
     : m_parent(parent), m_env(idx)
   {}
 
@@ -235,7 +235,7 @@ namespace core
     m_commands.ProcessList([this] (list<shared_ptr<CommandsQueue::Command> > & l) { ClearImpl(l); });
   }
 
-  int CommandsQueue::ExecutorsCount() const
+  size_t CommandsQueue::ExecutorsCount() const
   {
     return m_executorsCount;
   }
diff --git a/base/commands_queue.hpp b/base/commands_queue.hpp
index d3a099bdd4..a8d68b258d 100644
--- a/base/commands_queue.hpp
+++ b/base/commands_queue.hpp
@@ -30,15 +30,15 @@ namespace core
     class Environment : public my::Cancellable
     {
     private:
-      int m_threadNum;
+      size_t m_threadNum;
 
     protected:
-      explicit Environment(int threadNum);
+      explicit Environment(size_t threadNum);
 
       friend class Routine;
 
     public:
-      int threadNum() const; //< number of the thread, which is executing the commands
+      size_t threadNum() const; //< number of the thread, which is executing the commands
     };
 
     /// single commmand
@@ -121,7 +121,7 @@ namespace core
 
     public:
 
-      Routine(CommandsQueue * parent, int idx);
+      Routine(CommandsQueue * parent, size_t idx);
 
       void Do();
       void Cancel();
@@ -163,7 +163,7 @@ namespace core
     ~CommandsQueue();
 
     /// Number of executors in this queue
-    int ExecutorsCount() const;
+    size_t ExecutorsCount() const;
 
     /// Adding different types of commands
     /// @{