diff --git a/gwsumm/data/spectral.py b/gwsumm/data/spectral.py
index 48c9109b..a5323a3b 100644
--- a/gwsumm/data/spectral.py
+++ b/gwsumm/data/spectral.py
@@ -239,12 +239,13 @@ def _get_spectrogram(channel, segments, config=None, cache=None,
 def add_spectrogram(specgram, key=None, coalesce=True):
     """Add a `Spectrogram` to the global memory cache
     """
-    if key is None:
-        key = specgram.name or str(specgram.channel)
-    globalv.SPECTROGRAMS.setdefault(key, SpectrogramList())
-    globalv.SPECTROGRAMS[key].append(specgram)
-    if coalesce:
-        globalv.SPECTROGRAMS[key].coalesce()
+    if not numpy.any(numpy.isnan(specgram)):
+        if key is None:
+            key = specgram.name or str(specgram.channel)
+        globalv.SPECTROGRAMS.setdefault(key, SpectrogramList())
+        globalv.SPECTROGRAMS[key].append(specgram)
+        if coalesce:
+            globalv.SPECTROGRAMS[key].coalesce()
 
 
 @use_segmentlist