diff --git a/schemas/EGA.common.json b/schemas/EGA.common.json
index 6d548b46..3eef6e03 100644
--- a/schemas/EGA.common.json
+++ b/schemas/EGA.common.json
@@ -254,7 +254,7 @@
             ]
         },
         "SpotDescriptorType": {
-            "type": "array",
+            "type": "object",
             "title": "Spot descriptor",
             "description": "The 'SpotDescriptorType' specifies how to decode the individual reads of interest from the monolithic spot sequence. The spot descriptor contains aspects of the experimental design, platform, and processing information. There will be two methods of specification: one will be an index into a table of typical decodings, the other being an exact specification. This construct is needed for loading data and for interpreting the loaded sequencing assays. It can be omitted if the loader can infer read layout (from multiple input files or from one input files).",
             "required": ["SPOT_DECODE_SPEC"],