diff --git a/gr-analog/python/analog/wfm_tx.py b/gr-analog/python/analog/wfm_tx.py
index 70e91f82616..241242814d8 100644
--- a/gr-analog/python/analog/wfm_tx.py
+++ b/gr-analog/python/analog/wfm_tx.py
@@ -51,12 +51,12 @@ def __init__(self, audio_rate, quad_rate, tau=75e-6, max_dev=75e3, fh=-1.0):
 
         if do_interp:
             interp_factor = quad_rate // audio_rate
-            interp_taps = filter.optfir.low_pass(interp_factor,   # gain
-                                                 quad_rate,       # Fs
-                                                 16000,           # passband cutoff
-                                                 18000,           # stopband cutoff
-                                                 0.1,             # passband ripple dB
-                                                 40)              # stopband atten dB
+            interp_taps = filter.optfir.low_pass(interp_factor,  # gain
+                                                 quad_rate,  # Fs
+                                                 16000,  # passband cutoff
+                                                 18000,  # stopband cutoff
+                                                 0.1,  # passband ripple dB
+                                                 40)  # stopband atten dB
 
             print("len(interp_taps) =", len(interp_taps))
             self.interpolator = filter.interp_fir_filter_fff(