diff --git a/Log.mqh b/Log.mqh
index 8980772db..9e7781d31 100644
--- a/Log.mqh
+++ b/Log.mqh
@@ -256,7 +256,7 @@ class Log : public Object {
  }
  */
 
-  virtual string ToString() {
+  virtual const string ToString() {
     string result;
 
     unsigned int lid;
diff --git a/Market.mqh b/Market.mqh
index 388eee48c..b9a2bf9bc 100644
--- a/Market.mqh
+++ b/Market.mqh
@@ -245,7 +245,7 @@ class Market : public SymbolInfo {
   /**
    * Returns Market data in textual representation.
    */
-  string ToString() {
+  string const ToString() {
     return StringFormat(string("Pip digits/value: %d/%g, Spread: %d pts (%g pips; %.4f%%), Pts/pip: %d, ") +
                             "Volume digits: %d, " + "Delta: %g, Last change: %g pips",
                         GetPipDigits(), GetPipValue(), GetSpreadInPts(), GetSpreadInPips(), GetSpreadInPct(),
diff --git a/Object.mqh b/Object.mqh
index afe03ec3d..4d79f0343 100644
--- a/Object.mqh
+++ b/Object.mqh
@@ -127,14 +127,14 @@ class Object : public Dynamic {
     /**
      * Returns text representation of the object.
      */
-    virtual string ToString() {
+    virtual const string ToString() {
       return StringFormat("[Object #%04x]", GetPointer(this));
     }
 
     /**
      * Returns text representation of the object.
      */
-    virtual string ToJSON() {
+    virtual const string ToJSON() {
       return StringFormat("{ \"type\": \"%s\" }", typename(this));
     }
 
diff --git a/Order.mqh b/Order.mqh
index dad74daad..e961061f7 100644
--- a/Order.mqh
+++ b/Order.mqh
@@ -2733,7 +2733,7 @@ class Order : public SymbolInfo {
   /**
    * Returns order details in text.
    */
-  string ToString() {
+  string const ToString() {
     SerializerConverter stub(Serializer::MakeStubObject<Order>(SERIALIZER_FLAG_SKIP_HIDDEN));
     return SerializerConverter::FromObject(THIS_REF, SERIALIZER_FLAG_SKIP_HIDDEN)
         .ToString<SerializerJson>(SERIALIZER_FLAG_SKIP_HIDDEN, &stub);
diff --git a/Strategy.mqh b/Strategy.mqh
index 0865112ce..bb2c24374 100644
--- a/Strategy.mqh
+++ b/Strategy.mqh
@@ -907,7 +907,7 @@ class Strategy : public Object {
   /**
    * Prints strategy's details.
    */
-  string ToString() { return StringFormat("%s: %s", GetName(), sparams.ToString()); }
+  string const ToString() { return StringFormat("%s: %s", GetName(), sparams.ToString()); }
 
   /* Virtual methods */
 
diff --git a/SymbolInfo.mqh b/SymbolInfo.mqh
index 3ace24b22..d4f1957ec 100644
--- a/SymbolInfo.mqh
+++ b/SymbolInfo.mqh
@@ -502,7 +502,7 @@ class SymbolInfo : public Object {
   /**
    * Returns symbol information in string format.
    */
-  string ToString() {
+  const string ToString() {
     return StringFormat(
         string("Symbol: %s, Last Ask/Bid: %g/%g, Last Price/Session Volume: %d/%g, Point size: %g, Pip size: %g, ") +
             "Tick size: %g (%g pts), Tick value: %g (%g/%g), " + "Digits: %d, Spread: %d pts, Trade stops level: %d, " +
@@ -517,7 +517,7 @@ class SymbolInfo : public Object {
   /**
    * Returns symbol information in CSV format.
    */
-  string ToCSV(bool _header = false) {
+  const string ToCSV(bool _header = false) {
     return !_header
                ? StringFormat(string("%s,%g,%g,%d,%g,%g,%g,") + "%g,%g,%g,%g,%g," + "%d,%d,%d," + "%g,%g,%g,%g," +
                                   "%d,%g,%g,%d,%g,%g",
@@ -537,7 +537,7 @@ class SymbolInfo : public Object {
   /**
    * Returns serialized representation of the object instance.
    */
-  SerializerNodeType Serialize(Serializer &_s) {
+  const SerializerNodeType Serialize(Serializer &_s) {
     _s.Pass(THIS_REF, "symbol", symbol);
     _s.PassStruct(THIS_REF, "symbol-entry", s_entry);
     return SerializerNodeObject;
diff --git a/Timer.mqh b/Timer.mqh
index 528ec9d28..e772306d7 100644
--- a/Timer.mqh
+++ b/Timer.mqh
@@ -146,7 +146,7 @@ class Timer : public Object {
     /**
      * Print timer times.
      */
-    virtual string ToString() {
+    virtual const string ToString() {
       return StringFormat("%s(%d)=%d-%dms,med=%dms,sum=%dms",
         GetName(),
         ArraySize(this.data),