diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+# v1.0.5.0
+
+## Non-breaking
+
+- Added `sendQueryParams` specs covering a parameter list longer than 65535: `libpq` rejects it locally, without writing anything to the socket, both standalone and in the middle of a pipeline where the commands surrounding it must still get dispatched and drained without desync. `pqi-native` 1.0.1.3 fails both, encoding the parameter count as a wrapping 16-bit field instead of validating it, which corrupted the `Bind` message and desynchronized the connection; 1.0.1.4 fixes it. Found via `hasql` issue #326.
+
 # v1.0.4.0
 
 ## Non-breaking
diff --git a/pqi-conformance.cabal b/pqi-conformance.cabal
--- a/pqi-conformance.cabal
+++ b/pqi-conformance.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: pqi-conformance
-version: 1.0.4.0
+version: 1.0.5.0
 category: Database, PostgreSQL, Testing
 synopsis: Differential conformance tests for pqi adapters
 description:
diff --git a/src/library/Pqi/Conformance/Operation/SendQueryParams.hs b/src/library/Pqi/Conformance/Operation/SendQueryParams.hs
--- a/src/library/Pqi/Conformance/Operation/SendQueryParams.hs
+++ b/src/library/Pqi/Conformance/Operation/SendQueryParams.hs
@@ -9,7 +9,7 @@
 import qualified Pqi as Lq
 import Pqi.Conformance.Harness
 import Pqi.Conformance.Prelude
-import Pqi.Conformance.Scenario (drainResults, int4Oid)
+import Pqi.Conformance.Scenario (drainResults, execScenario, int4Oid, takeCommandResults, takeResult)
 import Test.Hspec
 
 spec :: Pqi.Adapter -> SpecWith ByteString
@@ -54,3 +54,38 @@
         results <- drainResults connection
         exited <- Lq.exitPipelineMode connection
         pure (entered, sentSelect, sentPrepare, sentQuery, synced, results, exited)
+
+    -- @PQsendQueryParams@ rejects a parameter list longer than 65535 (the
+    -- limit imposed by the wire protocol's 16-bit parameter count field)
+    -- locally, without writing anything to the socket: it returns 'False'
+    -- and leaves the connection exactly as usable as before the call.
+    --
+    -- <https://github.com/nikita-volkov/hasql/issues/326>
+    it "rejects a parameter list longer than 65535 without sending anything, leaving the connection usable" \conninfo ->
+      differential adapter conninfo \connection -> do
+        let overflowingParams = replicate 65536 (Just (int4Oid, "1", Lq.Text))
+        sent <- Lq.sendQueryParams connection "select 1 :: int4" overflowingParams Lq.Text
+        followUp <- execScenario "select 2 :: int4" connection
+        pure (sent, followUp)
+
+    -- The same rejection placed in the middle of a pipeline: the commands
+    -- before it must still get dispatched and the commands after it must
+    -- still get queued, with no desync in the result stream and no lasting
+    -- effect on the connection once the pipeline is torn down.
+    it "in a pipeline, a rejected send is skipped without desyncing the surrounding commands" \conninfo ->
+      differential adapter conninfo \connection -> do
+        let overflowingParams = replicate 65536 (Just (int4Oid, "1", Lq.Text))
+        entered <- Lq.enterPipelineMode connection
+        sentBefore1 <- Lq.sendQueryParams connection "select 1 :: int4" [] Lq.Text
+        sentBefore2 <- Lq.sendQueryParams connection "select 2 :: int4" [] Lq.Text
+        sentBad <- Lq.sendQueryParams connection "select 3 :: int4" overflowingParams Lq.Text
+        sentAfter <- Lq.sendQueryParams connection "select 4 :: int4" [] Lq.Text
+        synced <- Lq.pipelineSync connection
+        first <- takeCommandResults connection
+        second <- takeCommandResults connection
+        third <- takeCommandResults connection
+        syncResult <- takeResult connection
+        idle <- takeResult connection
+        exited <- Lq.exitPipelineMode connection
+        followUp <- execScenario "select 5 :: int4" connection
+        pure (entered, sentBefore1, sentBefore2, sentBad, sentAfter, synced, first, second, third, syncResult, idle, exited, followUp)