diff --git a/__fixtures__/plpgsql-pretty/trigger-function.sql b/__fixtures__/plpgsql-pretty/trigger-function.sql
new file mode 100644
index 00000000..a8e1ea7c
--- /dev/null
+++ b/__fixtures__/plpgsql-pretty/trigger-function.sql
@@ -0,0 +1,22 @@
+CREATE FUNCTION trigger_with_special_vars() RETURNS trigger
+LANGUAGE plpgsql
+AS $$
+BEGIN
+    IF TG_OP = 'INSERT' THEN
+        NEW.created_at := now();
+        RETURN NEW;
+    ELSIF TG_OP = 'UPDATE' THEN
+        IF OLD.id IS DISTINCT FROM NEW.id THEN
+            RAISE EXCEPTION 'IMMUTABLE_FIELD';
+        END IF;
+        NEW.updated_at := now();
+        RETURN NEW;
+    ELSIF TG_OP = 'DELETE' THEN
+        RETURN OLD;
+    END IF;
+    IF NOT FOUND THEN
+        RAISE EXCEPTION 'NOT_FOUND';
+    END IF;
+    RETURN NEW;
+END;
+$$
diff --git a/packages/plpgsql-deparser/__tests__/pretty/__snapshots__/plpgsql-pretty.test.ts.snap b/packages/plpgsql-deparser/__tests__/pretty/__snapshots__/plpgsql-pretty.test.ts.snap
index afe0e983..23713970 100644
--- a/packages/plpgsql-deparser/__tests__/pretty/__snapshots__/plpgsql-pretty.test.ts.snap
+++ b/packages/plpgsql-deparser/__tests__/pretty/__snapshots__/plpgsql-pretty.test.ts.snap
@@ -208,6 +208,27 @@ exports[`lowercase: simple-function.sql 1`] = `
 end"
 `;
 
+exports[`lowercase: trigger-function.sql 1`] = `
+"begin
+  if TG_OP = 'INSERT' then
+      NEW.created_at := now();
+      return NEW;
+  elsif TG_OP = 'UPDATE' then
+      if OLD.id IS DISTINCT FROM NEW.id then
+            raise exception 'IMMUTABLE_FIELD';
+      end if;
+      NEW.updated_at := now();
+      return NEW;
+  elsif TG_OP = 'DELETE' then
+      return OLD;
+  end if;
+  if NOT FOUND then
+      raise exception 'NOT_FOUND';
+  end if;
+  return NEW;
+end"
+`;
+
 exports[`uppercase: big-function.sql 1`] = `
 "DECLARE
   v_orders_scanned int := 0;
@@ -415,3 +436,24 @@ exports[`uppercase: simple-function.sql 1`] = `
   RETURN a + b;
 END"
 `;
+
+exports[`uppercase: trigger-function.sql 1`] = `
+"BEGIN
+  IF TG_OP = 'INSERT' THEN
+      NEW.created_at := now();
+      RETURN NEW;
+  ELSIF TG_OP = 'UPDATE' THEN
+      IF OLD.id IS DISTINCT FROM NEW.id THEN
+            RAISE EXCEPTION 'IMMUTABLE_FIELD';
+      END IF;
+      NEW.updated_at := now();
+      RETURN NEW;
+  ELSIF TG_OP = 'DELETE' THEN
+      RETURN OLD;
+  END IF;
+  IF NOT FOUND THEN
+      RAISE EXCEPTION 'NOT_FOUND';
+  END IF;
+  RETURN NEW;
+END"
+`;
diff --git a/packages/plpgsql-deparser/__tests__/pretty/plpgsql-pretty.test.ts b/packages/plpgsql-deparser/__tests__/pretty/plpgsql-pretty.test.ts
index 1cf7c434..be593b73 100644
--- a/packages/plpgsql-deparser/__tests__/pretty/plpgsql-pretty.test.ts
+++ b/packages/plpgsql-deparser/__tests__/pretty/plpgsql-pretty.test.ts
@@ -5,6 +5,7 @@ const prettyTest = new PlpgsqlPrettyTest([
   'simple-function.sql',
   'if-else-function.sql',
   'loop-function.sql',
+  'trigger-function.sql',
 ]);
 
 prettyTest.generateTests();