diff --git a/include/fintamath/functions/IFunctionCRTP.hpp b/include/fintamath/functions/IFunctionCRTP.hpp
index 79d757058..c523e6405 100644
--- a/include/fintamath/functions/IFunctionCRTP.hpp
+++ b/include/fintamath/functions/IFunctionCRTP.hpp
@@ -14,20 +14,30 @@ class IFunctionCRTP_ : public IFunction {
 #undef I_MATH_OBJECT_CRTP
 
 public:
+  static constexpr auto getArgumentClassesStatic() {
+    return std::array{Args::getClassStatic()...};
+  }
+
   const std::vector<MathObjectClass> &getArgumentClasses() const final {
-    return argTypes;
+    constexpr auto argClassesArr = getArgumentClassesStatic();
+    static const std::vector<MathObjectClass> argClassesVect(argClassesArr.begin(), argClassesArr.end());
+    return argClassesVect;
   }
 
-  MathObjectClass getReturnClass() const final {
+  static constexpr MathObjectClass getReturnClassStatic() {
     return Return::getClassStatic();
   }
 
+  MathObjectClass getReturnClass() const final {
+    return getReturnClassStatic();
+  }
+
   bool doArgsMatch(const ArgumentRefVector &argVect) const override {
     if constexpr (Derived::isVariadicStatic()) {
       return doAnyArgsMatch(argVect);
     }
     else {
-      if (argVect.size() != argTypes.size()) {
+      if (argVect.size() != getArgumentClassesStatic().size()) {
         return false;
       }
 
@@ -96,9 +106,6 @@ class IFunctionCRTP_ : public IFunction {
     });
   }
 
-private:
-  inline static const ArgumentTypeVector argTypes = {Args::getClassStatic()...};
-
 private:
 #if !defined(I_FUNCTION_CRTP) && !defined(NDEBUG)
 };
diff --git a/include/fintamath/literals/constants/IConstantCRTP.hpp b/include/fintamath/literals/constants/IConstantCRTP.hpp
index 7d28d8c4e..8e1776ebb 100644
--- a/include/fintamath/literals/constants/IConstantCRTP.hpp
+++ b/include/fintamath/literals/constants/IConstantCRTP.hpp
@@ -14,10 +14,14 @@ class IConstantCRTP_ : public IConstant {
 #undef I_LITERAL_CRTP
 
 public:
-  MathObjectClass getReturnClass() const final {
+  static constexpr MathObjectClass getReturnClassStatic() {
     return Return::getClassStatic();
   }
 
+  MathObjectClass getReturnClass() const final {
+    return getReturnClassStatic();
+  }
+
 private:
 #if !defined(I_CONSTANT_CRTP) && !defined(NDEBUG)
 };