diff --git a/ouroboros-consensus/src/Ouroboros/Consensus/HardFork/History/Summary.hs b/ouroboros-consensus/src/Ouroboros/Consensus/HardFork/History/Summary.hs
index 4de7f246432..d9f3a16f655 100644
--- a/ouroboros-consensus/src/Ouroboros/Consensus/HardFork/History/Summary.hs
+++ b/ouroboros-consensus/src/Ouroboros/Consensus/HardFork/History/Summary.hs
@@ -494,8 +494,35 @@ instance SListI xs => Serialise (Summary xs) where
   encode (Summary eraSummaries) = encode (toList eraSummaries)
   decode = do
       eraSummaries <- decode
-      case Summary <$> nonEmptyFromList eraSummaries of
+      -- The sender might be running a newer version that is (statically) aware
+      -- of more eras (@xs@) than we are. In this case, we ignore the eras past
+      -- the final era we are aware of rather than failing to decode.
+      let knownEraSummaries = take numKnownEras eraSummaries
+
+          -- When we received as many summaries as known eras, the final end
+          -- bound must already be unbounded, in which case this is a no-op.
+          --
+          -- When we actually had to drop some unknown eras, the now final era
+          -- will have a bounded end bound, as it was followed by one or more
+          -- eras. In this case, we make that end bound unbounded, as is always
+          -- the case for the final era.
+          go | length knownEraSummaries == numKnownEras
+             = fixEndBound
+
+             -- Fewer end summaries than known eras, by definition the last one
+             -- will /not/ have an unbounded end bound. We don't have to modify.
+             | otherwise
+             = id
+
+      case Summary . go <$> nonEmptyFromList eraSummaries of
         Just summary -> return summary
-        Nothing      -> fail $
-          "Summary: expected between 1 and " <> show (lengthSList (Proxy @xs)) <>
-          " eras but got " <> show (length eraSummaries)
+        Nothing      -> fail "Summary: expected at least one era summary"
+    where
+      -- | The number of statically known eras.
+      numKnownEras :: Int
+      numKnownEras = lengthSList (Proxy @xs)
+
+      -- | Make the last era's end bound unbounded.
+      fixEndBound :: NonEmpty xs' EraSummary -> NonEmpty xs' EraSummary
+      fixEndBound (NonEmptyCons e es) = NonEmptyCons e (fixEndBound es)
+      fixEndBound (NonEmptyOne  e)    = NonEmptyOne  e { eraEnd = EraUnbounded }