diff --git a/src/main/java/com/metamx/datatypes/mmx/MmxAuctionSummary.java b/src/main/java/com/metamx/datatypes/mmx/MmxAuctionSummary.java
index 4bb380d..2614d8a 100644
--- a/src/main/java/com/metamx/datatypes/mmx/MmxAuctionSummary.java
+++ b/src/main/java/com/metamx/datatypes/mmx/MmxAuctionSummary.java
@@ -44,6 +44,7 @@ public class MmxAuctionSummary
   private final User user;
   private final List<MmxBidResponse> responses;
   private final Ext ext;
+  private final String radTechVersion;
 
   public MmxAuctionSummary(
       @JsonProperty("timestamp") String timestamp,
@@ -70,6 +71,7 @@ public MmxAuctionSummary(
     this.user = user;
     this.responses = responses;
     this.ext = ext;
+    this.radTechVersion = MmxAuctionSummary.class.getPackage().getImplementationVersion();
   }
 
   @JsonProperty
@@ -138,6 +140,12 @@ public Ext getExt()
     return ext;
   }
 
+  @JsonProperty("rad_tech_version")
+  public String getRadTechVersion()
+  {
+    return radTechVersion;
+  }
+
   public static Builder builder()
   {
     return new Builder();