diff --git a/handel/mapping.py b/handel/mapping.py
index be33e678fb69c04b1fdb5fc7a9ee55014b8e994e..faaa4825dd0bb855ec4ffff9cc46ea99647b5db7 100644
--- a/handel/mapping.py
+++ b/handel/mapping.py
@@ -89,6 +89,10 @@ def parse_mapping_buffer(raw):
             spectrum.dtype = spectrum_type
             current += size
 
+            # Discard garbage
+            if channel_id in spectrums[pixel]:
+                continue
+
             # Set data
             stats = stats_from_mapping_mode(stats_block[index])
             spectrums[pixel][channel_id] = spectrum