diff --git a/lib/active_record/pg_extensions/transaction.rb b/lib/active_record/pg_extensions/transaction.rb
index aac3d02..94826c4 100644
--- a/lib/active_record/pg_extensions/transaction.rb
+++ b/lib/active_record/pg_extensions/transaction.rb
@@ -14,6 +14,9 @@ def #{kind}(local: false)
           private def #{kind}=(timeout)
             return if @#{kind} == timeout
 
+            # must precede dirty!, which disables lazy connect; connecting after would discard this transaction
+            connection.connect! unless connection.connected?
+
             @#{kind} = timeout
             # If we have set an explicit timeout, the transaction has state that must be materialized
             # separately from any other transaction, so it cannot be `restartable`
diff --git a/spec/postgresql_adapter_spec.rb b/spec/postgresql_adapter_spec.rb
index b3dac06..7ca6599 100644
--- a/spec/postgresql_adapter_spec.rb
+++ b/spec/postgresql_adapter_spec.rb
@@ -437,6 +437,26 @@
     end
   end
 
+  describe "#statement_timeout= on a connection that hasn't been used yet" do
+    before { connection.disconnect! }
+
+    it "materializes the transaction against a live connection" do
+      expect do
+        connection.transaction do
+          connection.statement_timeout = 30
+          connection.select_value("SELECT 1")
+        end
+      end.not_to raise_error
+    end
+
+    it "still applies the timeout" do
+      connection.transaction do
+        connection.statement_timeout = 0.01
+        expect { connection.execute("SELECT pg_sleep(3)") }.to raise_error(ActiveRecord::QueryCanceled)
+      end
+    end
+  end
+
   describe "#rename_constraint" do
     around do |example|
       connection.dont_execute(&example)