diff --git a/ouroboros-consensus/src/Ouroboros/Consensus/Protocol/PBFT/ChainState.hs b/ouroboros-consensus/src/Ouroboros/Consensus/Protocol/PBFT/ChainState.hs
index c76ac1cae8a..49ed5693926 100644
--- a/ouroboros-consensus/src/Ouroboros/Consensus/Protocol/PBFT/ChainState.hs
+++ b/ouroboros-consensus/src/Ouroboros/Consensus/Protocol/PBFT/ChainState.hs
@@ -353,14 +353,15 @@ append :: forall c. PBftCrypto c
        -> PBftChainState c -> PBftChainState c
 append k n signer@(PBftSigner _ gk) PBftChainState{..} =
     assertInvariant k n $
-    pruneEBBsLT $
     PBftChainState {
         preAnchor  = preAnchor'
       , postAnchor = postAnchor'
       , preWindow  = preWindow'
       , inWindow   = inWindow'
       , counts     = updateCounts counts
-      , ebbs       = ebbs   -- NB this needs to be pruned
+        -- NOTE: 'pruneEBBsLT' is inlined here to avoid a strange space leak
+        -- that also goes away with @-O0@, see #1356.
+      , ebbs       = EbbMap $ Map.filter (>= anchorSlot') (unEbbMap ebbs)
       }
   where
     (preAnchor', postAnchor') =
@@ -381,6 +382,10 @@ append k n signer@(PBftSigner _ gk) PBftChainState{..} =
           , incrementKey gk
           )
 
+    anchorSlot' = case preAnchor' of
+      _ :|> anchorSigner -> At (pbftSignerSlotNo anchorSigner)
+      _otherwise         -> Origin
+
 -- | Rewind the state to the specified slot
 --
 -- This matches the semantics of 'rewindChainState' in 'OuroborosTag', in that