diff --git a/src/PYTHON/python_compat.h b/src/PYTHON/python_compat.h
index 775435ffd8..d1194056d8 100644
--- a/src/PYTHON/python_compat.h
+++ b/src/PYTHON/python_compat.h
@@ -20,13 +20,12 @@
 #if PY_MAJOR_VERSION == 2
 #if defined(_MSC_VER) || defined(__MINGW32__)
 #define PY_INT_FROM_LONG(X) PyLong_FromLongLong(X)
+#define PY_INT_AS_LONG(X) PyLong_AsLongLong(X)
+#define PY_LONG_FROM_STRING(X) std::stoll(X)
 #else
 #define PY_INT_FROM_LONG(X) PyInt_FromLong(X)
-#endif
-#if defined(_MSC_VER) || defined(__MINGW32__)
-#define PY_INT_AS_LONG(X) PyLong_AsLongLong(X)
-#else
 #define PY_INT_AS_LONG(X) PyInt_AsLong(X)
+#define PY_LONG_FROM_STRING(X) std::stol(X)
 #endif
 #define PY_STRING_FROM_STRING(X) PyString_FromString(X)
 #define PY_VOID_POINTER(X) PyCObject_FromVoidPtr((void *) X, nullptr)
@@ -35,13 +34,12 @@
 #elif PY_MAJOR_VERSION == 3
 #if defined(_MSC_VER) || defined(__MINGW32__)
 #define PY_INT_FROM_LONG(X) PyLong_FromLongLong(X)
+#define PY_INT_AS_LONG(X) PyLong_AsLongLong(X)
+#define PY_LONG_FROM_STRING(X) std::stoll(X)
 #else
 #define PY_INT_FROM_LONG(X) PyLong_FromLong(X)
-#endif
-#if defined(_MSC_VER) || defined(__MINGW32__)
-#define PY_INT_AS_LONG(X) PyLong_AsLongLong(X)
-#else
 #define PY_INT_AS_LONG(X) PyLong_AsLong(X)
+#define PY_LONG_FROM_STRING(X) std::stol(X)
 #endif
 #define PY_STRING_FROM_STRING(X) PyUnicode_FromString(X)
 #define PY_VOID_POINTER(X) PyCapsule_New((void *) X, nullptr, nullptr)
diff --git a/src/PYTHON/python_impl.cpp b/src/PYTHON/python_impl.cpp
index 87a57187bf..91e0a7abe5 100644
--- a/src/PYTHON/python_impl.cpp
+++ b/src/PYTHON/python_impl.cpp
@@ -341,7 +341,7 @@ void PythonImpl::invoke_function(int ifunc, char *result)
         if (!str)
           error->all(FLERR, "Could not evaluate Python function {} input variable: {}",
                      pfuncs[ifunc].name, pfuncs[ifunc].svalue[i]);
-        pValue = PY_INT_FROM_LONG(atoi(str));
+        pValue = PY_INT_FROM_LONG(PY_LONG_FROM_STRING(str));
       } else {
         pValue = PY_INT_FROM_LONG(pfuncs[ifunc].ivalue[i]);
       }
@@ -351,7 +351,7 @@ void PythonImpl::invoke_function(int ifunc, char *result)
         if (!str)
           error->all(FLERR, "Could not evaluate Python function {} input variable: {}",
                      pfuncs[ifunc].name, pfuncs[ifunc].svalue[i]);
-        pValue = PyFloat_FromDouble(atof(str));
+        pValue = PyFloat_FromDouble(std::stod(str));
       } else {
         pValue = PyFloat_FromDouble(pfuncs[ifunc].dvalue[i]);
       }