diff --git a/waveform_benchmark/formats/wfdb.py b/waveform_benchmark/formats/wfdb.py
index 5727ec8..48a1c5e 100644
--- a/waveform_benchmark/formats/wfdb.py
+++ b/waveform_benchmark/formats/wfdb.py
@@ -43,9 +43,12 @@ def write_waveforms(self, path, waveforms):
                 sig_samples[start:end] = chunk['samples']
                 sig_gain = max(sig_gain, chunk['gain'])
 
-            sample_min = numpy.nanmin(sig_samples)
-            sample_max = numpy.nanmax(sig_samples)
-            sig_baseline = round(-sig_gain * (sample_min + sample_max) / 2)
+            if all(numpy.isnan(sig_samples)):
+                sig_baseline = 0
+            else:
+                sample_min = numpy.nanmin(sig_samples)
+                sample_max = numpy.nanmax(sig_samples)
+                sig_baseline = round(-sig_gain * (sample_min + sample_max) / 2)
             adc_gain.append(sig_gain)
             baseline.append(sig_baseline)
             e_p_signal.append(sig_samples)