diff --git a/gamutrf/grscan.py b/gamutrf/grscan.py
index 49a6e4d8..bf8cd97c 100644
--- a/gamutrf/grscan.py
+++ b/gamutrf/grscan.py
@@ -73,7 +73,9 @@ def __init__(
         self.wavelearner = wavelearner
         self.iqtlabs = iqtlabs
         self.samp_rate = samp_rate
-        self.retune_pre_fft = None
+        self.retune_pre_fft = blocks.stream_to_vector(
+            gr.sizeof_gr_complex, fft_batch_size * nfft
+        )
 
         ##################################################
         # Blocks
@@ -305,26 +307,8 @@ def get_offload_fft_block(
         tuning_ranges,
         pretune,
     ):
-        if pretune:
-            self.retune_pre_fft = self.iqtlabs.retune_pre_fft(
-                nfft,
-                fft_batch_size,
-                "rx_freq",
-                int(freq_start),
-                int(freq_end),
-                tune_step_hz,
-                tune_step_fft,
-                skip_tune_step,
-                tuning_ranges,
-            )
-            stream_to_vector = self.retune_pre_fft
-        else:
-            stream_to_vector = blocks.stream_to_vector(
-                gr.sizeof_gr_complex, fft_batch_size * nfft
-            )
-
         offload_blocks = [
-            stream_to_vector,
+            self.retune_pre_fft,
             blocks.multiply_const_vff(
                 [val for val in self.get_window(nfft) for _ in range(2)]
                 * fft_batch_size
@@ -351,6 +335,18 @@ def get_fft_blocks(
         tuning_ranges,
         pretune,
     ):
+        if pretune:
+            self.retune_pre_fft = self.iqtlabs.retune_pre_fft(
+                nfft,
+                fft_batch_size,
+                "rx_freq",
+                int(freq_start),
+                int(freq_end),
+                tune_step_hz,
+                tune_step_fft,
+                skip_tune_step,
+                tuning_ranges,
+            )
         fft_blocks = []
         if dc_block_len:
             fft_blocks.append(grfilter.dc_blocker_cc(dc_block_len, dc_block_long))
@@ -380,7 +376,7 @@ def get_fft_blocks(
         else:
             fft_blocks.extend(
                 [
-                    blocks.stream_to_vector(gr.sizeof_gr_complex, nfft),
+                    self.retune_pre_fft,
                     fft.fft_vcc(nfft, True, self.get_window(nfft), True, 1),
                 ]
             )
diff --git a/tests/test_grscan.py b/tests/test_grscan.py
index 2a180db8..a102dccd 100644
--- a/tests/test_grscan.py
+++ b/tests/test_grscan.py
@@ -95,7 +95,7 @@ def test_get_source_smoke(self):
         for sdr in ("ettus", "bladerf"):
             self.assertRaises(RuntimeError, get_source, sdr, 1e3, 10)
 
-    def run_grscan_smoke(self, wavelearner, write_samples):
+    def run_grscan_smoke(self, pretune, wavelearner, write_samples):
         with tempfile.TemporaryDirectory() as tempdir:
             tb = grscan(
                 sdr="tuneable_test_source",
@@ -106,9 +106,11 @@ def run_grscan_smoke(self, wavelearner, write_samples):
                 wavelearner=wavelearner,
                 rotate_secs=900,
                 db_clamp_floor=-1e6,
+                pretune=pretune,
+                fft_batch_size=1,
             )
             tb.start()
-            time.sleep(10)
+            time.sleep(3)
             tb.stop()
             tb.wait()
             del tb
@@ -118,13 +120,10 @@ def run_grscan_smoke(self, wavelearner, write_samples):
             self.assertTrue([x for x in glob.glob(f"{tempdir}/*/*sigmf-meta")])
 
     def test_grscan_smoke(self):
-        for wavelearner, write_samples in (
-            (None, 0),
-            (None, 1),
-            (FakeWaveLearner(), 0),
-            (FakeWaveLearner(), 1),
-        ):
-            self.run_grscan_smoke(wavelearner, write_samples)
+        for pretune in (True, False):
+            for wavelearner in (FakeWaveLearner(), None):
+                for write_samples in (0, 1):
+                    self.run_grscan_smoke(pretune, wavelearner, write_samples)
 
 
 if __name__ == "__main__":  # pragma: no cover