diff --git a/library/src/commonMain/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/BooleanExpressionBuilder.kt b/library/src/commonMain/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/BooleanExpressionBuilder.kt
index f72df21..9296854 100644
--- a/library/src/commonMain/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/BooleanExpressionBuilder.kt
+++ b/library/src/commonMain/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/BooleanExpressionBuilder.kt
@@ -50,8 +50,6 @@ internal class BooleanExpressionBuilder<I : Matcher<T>, T> {
         {
             node = node.parent!!
         }
-
-        node.flatten()
     }
 
     fun addValue(i: I) {
diff --git a/library/src/commonTest/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/TagFilterExpressionParserTest.kt b/library/src/commonTest/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/TagFilterExpressionParserTest.kt
index 4861cbf..6af6e7b 100644
--- a/library/src/commonTest/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/TagFilterExpressionParserTest.kt
+++ b/library/src/commonTest/kotlin/de/westnordost/osm_legal_default_speeds/tagfilter/TagFilterExpressionParserTest.kt
@@ -458,7 +458,16 @@ internal class TagFilterExpressionParserTest {
         notMatches(mapOfKeys("a", "b", "c", "d"), expr)
     }
 
-
+    @Test fun brackets_are_not_dissolved_illegally() {
+        val expr = "a or (b or c) and !d"
+        matches(mapOfKeys("a"), expr)
+        matches(mapOfKeys("a", "d"), expr)
+        matches(mapOfKeys("b"), expr)
+        matches(mapOfKeys("c"), expr)
+        notMatches(mapOfKeys("c", "d"), expr)
+        notMatches(mapOfKeys("b", "d"), expr)
+        matches(mapOfKeys("a", "c", "d"), expr)
+    }
 
     @Test fun fail_on_placeholder_not_closed() {
         shouldFail("{my placeholder")