diff --git a/src/fintamath/expressions/unary/HyperbExpression.cpp b/src/fintamath/expressions/unary/HyperbExpression.cpp
index 2d2cc361a..63c97c2d8 100644
--- a/src/fintamath/expressions/unary/HyperbExpression.cpp
+++ b/src/fintamath/expressions/unary/HyperbExpression.cpp
@@ -48,12 +48,7 @@ std::shared_ptr<IFunction> HyperbExpression::getOppositeFunction(const IFunction
       {Tanh().toString(), std::make_unique<Atanh>()}, //
       {Coth().toString(), std::make_unique<Acoth>()}, //
   };
-
-  if (auto res = oppositeFunctions.find(function.toString()); res != oppositeFunctions.end()) {
-    return res->second;
-  }
-
-  return {};
+  return oppositeFunctions.at(function.toString());
 }
 
 }
diff --git a/src/fintamath/expressions/unary/TrigExpression.cpp b/src/fintamath/expressions/unary/TrigExpression.cpp
index beec6f60a..497d1a674 100644
--- a/src/fintamath/expressions/unary/TrigExpression.cpp
+++ b/src/fintamath/expressions/unary/TrigExpression.cpp
@@ -54,11 +54,7 @@ std::shared_ptr<IFunction> TrigExpression::getOppositeFunction(const IFunction &
       {Tan().toString(), std::make_shared<Atan>()}, //
       {Cot().toString(), std::make_shared<Acot>()}, //
   };
-
-  if (auto res = oppositeFunctions.find(function.toString()); res != oppositeFunctions.end()) {
-    return res->second;
-  }
-
-  return {};
+  return oppositeFunctions.at(function.toString());
 }
+
 }