diff --git a/README.md b/README.md
index e68223d..ce09572 100644
--- a/README.md
+++ b/README.md
@@ -81,8 +81,8 @@ Or with pattern matching:
 case event_store.append([En57::Event.new(type: "OrderPlaced")])
 in En57::Result::Success(position:)
   puts "appended up to #{position}"
-in En57::Result::Failure
-  puts "append condition violated"
+in En57::Result::Failure(position:, conflicting_events:)
+  puts "blocked by #{conflicting_events.size} event(s) up to position #{position}"
 end
 ```
 
@@ -138,7 +138,7 @@ result = event_store.append(
 )
 
 if result.failure?
-  # lost the race; another writer already consumed credits
+  # lost the race; result.conflicting_events shows what got there first
 end
 ```
 
@@ -173,6 +173,6 @@ result = event_store.append(
 )
 
 if result.failure?
-  # email already used
+  # email already used; result.conflicting_events lists the prior registration(s)
 end
 ```
diff --git a/db/schema/0.1.0.sql b/db/schema/0.1.0.sql
index e2de6a0..d7d03dd 100644
--- a/db/schema/0.1.0.sql
+++ b/db/schema/0.1.0.sql
@@ -27,7 +27,7 @@ CREATE TYPE en57.event AS (
 );
 
 CREATE FUNCTION en57.append_events (new_events en57.event[], append_condition jsonb DEFAULT '{}'::jsonb)
-    RETURNS TABLE ("position" bigint)
+    RETURNS TABLE ("position" bigint, conflicting_events text)
     LANGUAGE plpgsql
     AS $$
 #variable_conflict use_column
@@ -35,20 +35,28 @@ DECLARE
     criteria jsonb[] := ARRAY (
         SELECT
             jsonb_array_elements(COALESCE(append_condition -> 'fail_if_events_match', '[]'::jsonb)));
+    conflicts jsonb;
+    conflict_max_position bigint;
     last_position bigint;
 BEGIN
-    IF cardinality(criteria) > 0 AND EXISTS (
-        SELECT
-            1
-        FROM
-            en57.events AS e
-        WHERE
-            EXISTS (
+    IF cardinality(criteria) > 0 THEN
+        WITH matches AS (
             SELECT
-                1
+                e.position,
+                jsonb_build_object('id', e.id, 'type', e.type, 'data', e.data::text, 'meta', e.meta::text, 'tags', COALESCE((
+                    SELECT
+                        array_agg(t.value ORDER BY t.value) FROM en57.tags AS t
+                    WHERE
+                        t.event_id = e.id), ARRAY[]::text[])) AS event_obj
             FROM
-                unnest(criteria) AS c
-            WHERE ((c ->> 'after')::bigint IS NULL OR e.position > (c ->> 'after')::bigint) AND (c -> 'types' IS NULL OR e.type IN (
+                en57.events AS e
+            WHERE
+                EXISTS (
+                    SELECT
+                        1
+                    FROM
+                        unnest(criteria) AS c
+                    WHERE ((c ->> 'after')::bigint IS NULL OR e.position > (c ->> 'after')::bigint) AND (c -> 'types' IS NULL OR e.type IN (
 SELECT
     jsonb_array_elements_text(c -> 'types'))) AND NOT EXISTS (
 SELECT
@@ -62,8 +70,18 @@ WHERE
     FROM
         en57.tags AS t
     WHERE
-        t.event_id = e.id AND t.value = req.value)))) THEN
-        RAISE EXCEPTION 'append_condition_violated';
+        t.event_id = e.id AND t.value = req.value)))
+)
+        SELECT
+            max(position),
+            jsonb_agg(event_obj ORDER BY position) INTO conflict_max_position,
+            conflicts
+        FROM
+            matches;
+        IF conflict_max_position IS NOT NULL THEN
+            RETURN QUERY SELECT conflict_max_position, conflicts::text;
+            RETURN;
+        END IF;
     END IF;
     WITH inserted AS (
         INSERT INTO en57.events (id, type, data, meta)
@@ -84,7 +102,7 @@ WHERE
     FROM
         unnest(new_events) AS e
     CROSS JOIN LATERAL unnest(COALESCE(e.tags, ARRAY[]::text[])) AS t (value);
-    RETURN QUERY SELECT last_position;
+    RETURN QUERY SELECT last_position, '[]'::text;
 END;
 $$;
 
diff --git a/lib/en57/repository.rb b/lib/en57/repository.rb
index 4d1c1d1..09ee4a5 100644
--- a/lib/en57/repository.rb
+++ b/lib/en57/repository.rb
@@ -32,20 +32,42 @@ module En57
         :fail_if_events_match
       ] = fail_if_events_match unless fail_if_events_match.empty?
 
-      result =
-        @adapter.with_serializable_transaction do |connection|
-          connection.exec_params(
-            "SELECT position FROM en57.append_events($1::en57.event[], $2::jsonb)",
-            [
-              @array_encoder.encode(event_records),
-              JSON.generate(append_condition),
-            ],
-          )
-        end
-      position = result.first.fetch("position")
-      Result.success(position: position && Integer(position))
-    rescue PG::RaiseException, PG::TRSerializationFailure
-      Result.failure(position: nil)
+      row =
+        @adapter
+          .with_serializable_transaction do |connection|
+            connection.exec_params(
+              "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
+              [
+                @array_encoder.encode(event_records),
+                JSON.generate(append_condition),
+              ],
+            )
+          end
+          .first
+      raw_position = row.fetch("position")
+      position = raw_position && Integer(raw_position)
+      conflicting_events =
+        JSON
+          .parse(row.fetch("conflicting_events"))
+          .map do |conflict|
+            Event.new(
+              id: conflict.fetch("id"),
+              type: conflict.fetch("type"),
+              data:
+                @serializer.load(
+                  conflict.fetch("data") || "{}",
+                  conflict.fetch("meta"),
+                ),
+              tags: conflict.fetch("tags"),
+            )
+          end
+      if conflicting_events.empty?
+        Result.success(position:)
+      else
+        Result.failure(position:, conflicting_events:)
+      end
+    rescue PG::TRSerializationFailure
+      Result.failure(position: nil, conflicting_events: [])
     end
 
     def read(query)
diff --git a/lib/en57/result.rb b/lib/en57/result.rb
index 6b73232..e3a7662 100644
--- a/lib/en57/result.rb
+++ b/lib/en57/result.rb
@@ -9,13 +9,14 @@ module En57
       end
 
     Failure =
-      Data.define(:position) do
+      Data.define(:position, :conflicting_events) do
         def success? = false
         def failure? = true
       end
 
     def self.success(position:) = Success.new(position:)
 
-    def self.failure(position:) = Failure.new(position:)
+    def self.failure(position:, conflicting_events:) =
+      Failure.new(position:, conflicting_events:)
   end
 end
diff --git a/test/test_integration.rb b/test/test_integration.rb
index 4f5f956..06cd71d 100644
--- a/test/test_integration.rb
+++ b/test/test_integration.rb
@@ -67,7 +67,9 @@ module En57
               fail_if: event_store.read.of_type("OrderPlaced"),
             )
 
-          assert(result.failure?)
+          assert(Result::Failure === result)
+          assert_equal(1, result.position)
+          assert_equal([existing_event], result.conflicting_events)
           assert_equal([existing_event], event_store.read.each.to_a)
         end
       end
diff --git a/test/test_repository.rb b/test/test_repository.rb
index f301327..6c42ff2 100644
--- a/test/test_repository.rb
+++ b/test/test_repository.rb
@@ -34,9 +34,9 @@ module En57
         connection.expect(:exec, nil, ["BEGIN ISOLATION LEVEL SERIALIZABLE"])
         connection.expect(
           :exec_params,
-          [{ "position" => "2" }],
+          [{ "position" => "2", "conflicting_events" => "[]" }],
           [
-            "SELECT position FROM en57.append_events($1::en57.event[], $2::jsonb)",
+            "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
             [expected_events, "{}"],
           ],
         )
@@ -81,9 +81,9 @@ module En57
         connection.expect(:exec, nil, ["BEGIN ISOLATION LEVEL SERIALIZABLE"])
         connection.expect(
           :exec_params,
-          [{ "position" => "1" }],
+          [{ "position" => "1", "conflicting_events" => "[]" }],
           [
-            "SELECT position FROM en57.append_events($1::en57.event[], $2::jsonb)",
+            "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
             [expected_events, "{}"],
           ],
         )
@@ -107,9 +107,9 @@ module En57
         connection.expect(:exec, nil, ["BEGIN ISOLATION LEVEL SERIALIZABLE"])
         connection.expect(
           :exec_params,
-          [{ "position" => nil }],
+          [{ "position" => nil, "conflicting_events" => "[]" }],
           [
-            "SELECT position FROM en57.append_events($1::en57.event[], $2::jsonb)",
+            "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
             [
               array_encoder.encode([]),
               '{"fail_if_events_match":[{"types":["OrderPlaced"],"after":42}]}',
@@ -146,7 +146,7 @@ module En57
         connection.expect(:exec, nil, ["ROLLBACK"])
         connection.expect(:exec_params, nil) do |sql, params|
           assert_equal(
-            "SELECT position FROM en57.append_events($1::en57.event[], $2::jsonb)",
+            "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
             sql,
           )
           assert_equal([array_encoder.encode([]), "{}"], params)
@@ -522,19 +522,76 @@ module En57
       end
     end
 
-    def test_append_returns_failure_on_pg_raise_exception
+    def test_append_returns_failure_when_condition_matches
       with_connection do |connection|
         connection.expect(:exec, nil, ["BEGIN ISOLATION LEVEL SERIALIZABLE"])
-        connection.expect(:exec, nil, ["ROLLBACK"])
-        connection.expect(:exec_params, nil) { raise(PG::RaiseException.new) }
+        connection.expect(
+          :exec_params,
+          [
+            {
+              "position" => "5",
+              "conflicting_events" =>
+                JSON.generate(
+                  [
+                    {
+                      id: ids[2],
+                      type: "OrderPlaced",
+                      data: '{"amount":100}',
+                      meta: '{"amount":{"k":"Symbol"}}',
+                      tags: ["order_id:123"],
+                    },
+                    {
+                      id: ids[3],
+                      type: "OrderPlaced",
+                      data: nil,
+                      meta: nil,
+                      tags: [],
+                    },
+                  ],
+                ),
+            },
+          ],
+          [
+            "SELECT position, conflicting_events FROM en57.append_events($1::en57.event[], $2::jsonb)",
+            [
+              array_encoder.encode([]),
+              '{"fail_if_events_match":[{"types":["OrderPlaced"]}]}',
+            ],
+          ],
+        )
+        connection.expect(:exec, nil, ["COMMIT"])
 
         result =
           Repository.new(
             PgAdapter.for_connection(connection),
             JsonSerializer.new,
-          ).append([], fail_if: Query.all)
+          ).append(
+            [],
+            fail_if:
+              Query.new(
+                criteria: [
+                  Query::Criteria.new(types: ["OrderPlaced"], tags: []),
+                ],
+              ),
+          )
 
-        assert_equal(Result.failure(position: nil), result)
+        assert_equal(
+          Result.failure(
+            position: 5,
+            conflicting_events: [
+              Event.new(
+                id: ids[2],
+                type: "OrderPlaced",
+                data: {
+                  amount: 100,
+                },
+                tags: ["order_id:123"],
+              ),
+              Event.new(id: ids[3], type: "OrderPlaced", data: {}, tags: []),
+            ],
+          ),
+          result,
+        )
       end
     end
 
@@ -552,7 +609,10 @@ module En57
             JsonSerializer.new,
           ).append([], fail_if: Query.all)
 
-        assert_equal(Result.failure(position: nil), result)
+        assert_equal(
+          Result.failure(position: nil, conflicting_events: []),
+          result,
+        )
       end
     end
 
diff --git a/test/test_result.rb b/test/test_result.rb
index 3834e84..6935c68 100644
--- a/test/test_result.rb
+++ b/test/test_result.rb
@@ -14,12 +14,14 @@ module En57
       assert_equal(42, result.position)
     end
 
-    def test_failure_carries_position
-      result = Result.failure(position: 7)
+    def test_failure_carries_position_and_conflicting_events
+      conflict = Event.new(type: "OrderPlaced")
+      result = Result.failure(position: 7, conflicting_events: [conflict])
 
       assert(result.failure?)
       refute(result.success?)
       assert_equal(7, result.position)
+      assert_equal([conflict], result.conflicting_events)
     end
   end
 end