diff --git a/src/ucioption.cpp b/src/ucioption.cpp
index 51987d03..75eb2053 100644
--- a/src/ucioption.cpp
+++ b/src/ucioption.cpp
@@ -33,10 +33,10 @@ OptionsMap Options; // Global object
 namespace {
 
 /// 'On change' actions, triggered by an option's value change
-void on_eval(UCIOption&) { Eval::init(); }
-void on_threads(UCIOption&) { Threads.read_uci_options(); }
-void on_hash_size(UCIOption& o) { TT.set_size(o); }
-void on_clear_hash(UCIOption& o) { TT.clear(); o = false; } // UCI button
+void on_eval(const UCIOption&) { Eval::init(); }
+void on_threads(const UCIOption&) { Threads.read_uci_options(); }
+void on_hash_size(const UCIOption& o) { TT.set_size(o); }
+void on_clear_hash(const UCIOption&) { TT.clear(); }
 
 /// Our case insensitive less() function as required by UCI protocol
 bool ci_less(char c1, char c2) { return tolower(c1) < tolower(c2); }
@@ -74,7 +74,7 @@ OptionsMap::OptionsMap() {
   o["Threads"]                     = UCIOption(cpus, 1, MAX_THREADS);
   o["Use Sleeping Threads"]        = UCIOption(true, on_threads);
   o["Hash"]                        = UCIOption(32, 4, 8192, on_hash_size);
-  o["Clear Hash"]                  = UCIOption(false, on_clear_hash);
+  o["Clear Hash"]                  = UCIOption(on_clear_hash);
   o["Ponder"]                      = UCIOption(true);
   o["OwnBook"]                     = UCIOption(true);
   o["MultiPV"]                     = UCIOption(1, 1, 500);
@@ -121,6 +121,9 @@ UCIOption::UCIOption(const char* v, Fn* f) : type("string"), min(0), max(0), idx
 UCIOption::UCIOption(bool v, Fn* f) : type("check"), min(0), max(0), idx(Options.size()), on_change(f)
 { defaultValue = currentValue = (v ? "true" : "false"); }
 
+UCIOption::UCIOption(Fn* f) : type("button"), min(0), max(0), idx(Options.size()), on_change(f)
+{ defaultValue = currentValue = "false"; }
+
 UCIOption::UCIOption(int v, int minv, int maxv, Fn* f) : type("spin"), min(minv), max(maxv), idx(Options.size()), on_change(f)
 { std::ostringstream ss; ss << v; defaultValue = currentValue = ss.str(); }
 
@@ -134,12 +137,15 @@ void UCIOption::operator=(const string& v) {
   assert(!type.empty());
 
   if (   !v.empty()
-      && (type == "check") == (v == "true" || v == "false")
+      && (type == "check" || type == "button") == (v == "true" || v == "false")
       && (type != "spin" || (atoi(v.c_str()) >= min && atoi(v.c_str()) <= max)))
   {
       currentValue = v;
 
       if (on_change)
           (*on_change)(*this);
+
+      if (type == "button")
+          currentValue = "false";
   }
 }
diff --git a/src/ucioption.h b/src/ucioption.h
index cde83231..7af54739 100644
--- a/src/ucioption.h
+++ b/src/ucioption.h
@@ -30,12 +30,12 @@ struct OptionsMap;
 /// UCIOption class implements an option as defined by UCI protocol
 class UCIOption {
 
-  typedef void (Fn)(UCIOption&);
+  typedef void (Fn)(const UCIOption&);
 
 public:
-  UCIOption() {} // Required by std::map::operator[]
-  UCIOption(const char* v, Fn* = NULL);
+  UCIOption(Fn* = NULL);
   UCIOption(bool v, Fn* = NULL);
+  UCIOption(const char* v, Fn* = NULL);
   UCIOption(int v, int min, int max, Fn* = NULL);
 
   void operator=(const std::string& v);