diff --git a/src/libs/qmuparser/qmutokenparser.cpp b/src/libs/qmuparser/qmutokenparser.cpp
index f32833e06..df538db5e 100644
--- a/src/libs/qmuparser/qmutokenparser.cpp
+++ b/src/libs/qmuparser/qmutokenparser.cpp
@@ -96,44 +96,10 @@ QmuTokenParser::QmuTokenParser(const QString &formula, bool osSeparator,
  */
 bool QmuTokenParser::IsSingle(const QString &formula)
 {
-    if (formula.isEmpty())
-    {
-        return false;// if don't know say no
-    }
-
-    QScopedPointer<QmuTokenParser> cal(new QmuTokenParser());
-
-    // Parser doesn't know any variable on this stage. So, we just use variable factory that for each unknown
-    // variable set value to 0.
-    cal->SetVarFactory(AddVariable, cal.data());
-    cal->SetSepForEval();//Reset separators options
-
-    try
-    {
-        cal->SetExpr(formula);
-        cal->Eval();// We don't need save result, only parse formula
-    }
-    catch (const qmu::QmuParserError &e)
-    {
-        Q_UNUSED(e)
-        return false;// something wrong with formula, say no
-    }
-
-    QMap<int, QString> tokens = cal->GetTokens();// Tokens (variables, measurements)
-    const QMap<int, QString> numbers = cal->GetNumbers();// All numbers in expression
-    delete cal.take();
-
-    // Remove "-" from tokens list if exist. If don't do that unary minus operation will broken.
-    RemoveAll(tokens, QStringLiteral("-"));
-
-    if (tokens.isEmpty() && numbers.size() == 1)
-    {
-        return true;
-    }
-    else
-    {
-        return false;
-    }
+    QLocale c(QLocale::C);
+    bool ok = false;
+    c.toDouble(formula, &ok);
+    return ok;
 }
 
 }// namespace qmu
diff --git a/src/test/ValentinaTest/tst_qmutokenparser.cpp b/src/test/ValentinaTest/tst_qmutokenparser.cpp
index 9f4758ff3..4002050a7 100644
--- a/src/test/ValentinaTest/tst_qmutokenparser.cpp
+++ b/src/test/ValentinaTest/tst_qmutokenparser.cpp
@@ -45,8 +45,10 @@ void TST_QmuTokenParser::IsSingle_data()
     QTest::addColumn<QString>("formula");
     QTest::addColumn<bool>("result");
 
+    QTest::newRow("Empty string") << "" << false;
     QTest::newRow("Single value") << "15.5" << true;
     QTest::newRow("Two digits") << "2+2" << false;
+    QTest::newRow("Two digits") << "2-2" << false;
     QTest::newRow("Negative single value") << "-2" << true;
     QTest::newRow("Digit and variable") << "2+a" << false;
     QTest::newRow("One variable twice") << "a+a" << false;
@@ -54,6 +56,7 @@ void TST_QmuTokenParser::IsSingle_data()
     QTest::newRow("Empty string") << "" << false;
     QTest::newRow("Several spaces") << "   " << false;
     QTest::newRow("Invalid formula") << "2*)))" << false;
+    QTest::newRow("Invalid formula") << "2*" << false;
     QTest::newRow("Incorrect thousand separator 15 500") << "15 500" << false;
     QTest::newRow("Correct C locale 15500") << "15500" << true;
     QTest::newRow("Correct C locale 15,500") << "15,500" << true;