diff --git a/pyroomacoustics/libroom_src/rir_builder.cpp b/pyroomacoustics/libroom_src/rir_builder.cpp
index 1c1ae92f..a2300263 100644
--- a/pyroomacoustics/libroom_src/rir_builder.cpp
+++ b/pyroomacoustics/libroom_src/rir_builder.cpp
@@ -324,22 +324,7 @@ void threaded_fractional_delay_impl(
   // relase the GIL from here on
   py::gil_scoped_release release;
 
-  for (size_t idx = 0; idx < n_times; idx++) {
-    // LUT interpolation
-    T x_off_frac = (1. - tim_acc(idx)) * lut_gran_f;
-    T lut_gran_off = std::floor(x_off_frac);
-    T x_off = (x_off_frac - lut_gran_off);
-
-    int lut_pos = int(lut_gran_off);
-    for (size_t k = 0; k < fdl; lut_pos += lut_gran, k++)
-      out_acc(idx, k) =
-          hann[k] *
-          (sinc_lut[lut_pos] +
-           x_off * (sinc_lut[lut_pos + 1] - sinc_lut[lut_pos]));
-  }
-
   // build the RIR
-  /*
   ThreadPool pool(num_threads);
   std::vector<std::future<void>> results;
   for (size_t t_idx = 0; t_idx < num_threads; t_idx++) {
@@ -366,7 +351,6 @@ void threaded_fractional_delay_impl(
   }
 
   for (auto &&result : results) result.get();
-  */
 }
 
 void fractional_delay(py::buffer out, const py::buffer time, size_t lut_gran,
diff --git a/pyroomacoustics/libroom_src/rir_builder.hpp b/pyroomacoustics/libroom_src/rir_builder.hpp
index fe7f3557..f4802a4c 100644
--- a/pyroomacoustics/libroom_src/rir_builder.hpp
+++ b/pyroomacoustics/libroom_src/rir_builder.hpp
@@ -17,6 +17,4 @@ void delay_sum(const py::buffer irs, const py::buffer delays, py::buffer output,
 void fractional_delay(py::buffer out, const py::buffer time, size_t lut_gran,
                       size_t num_threads);
 
-#include "rir_builder.cpp"
-
 #endif  // __RIR_BUILDER_HPP__
diff --git a/setup.py b/setup.py
index ece0b76b..a91a0746 100644
--- a/setup.py
+++ b/setup.py
@@ -60,7 +60,7 @@ def __str__(self):
 ext_modules = [
     Extension(
         "pyroomacoustics.libroom",
-        [os.path.join(libroom_src_dir, f) for f in ["libroom.cpp"]],
+        [os.path.join(libroom_src_dir, f) for f in ["libroom.cpp", "rir_builder.cpp"]],
         depends=libroom_files,
         include_dirs=[
             ".",