diff --git a/numerical_methods/fast_fourier_transform.cpp b/numerical_methods/fast_fourier_transform.cpp
index d8bc42d42..1b09831dd 100644
--- a/numerical_methods/fast_fourier_transform.cpp
+++ b/numerical_methods/fast_fourier_transform.cpp
@@ -80,6 +80,7 @@ std::complex<double> *FastFourierTransform(std::complex<double> *p,
     delete[] po; /// Deleting dynamic array po
     return y;  /// Returns the list
 }
+}  // namespace numerical_methods
 
 /**
  * @brief Self-test implementations