diff --git a/src/gui/widgets/timeline/timeline-layout-helper.cpp b/src/gui/widgets/timeline/timeline-layout-helper.cpp
index 2116641fc..d57baddc5 100644
--- a/src/gui/widgets/timeline/timeline-layout-helper.cpp
+++ b/src/gui/widgets/timeline/timeline-layout-helper.cpp
@@ -162,7 +162,7 @@ void
 TimelineLayoutHelper::layout_headers_recursive(
   TrackTree::iterator_base parent_iterator,
   int &offset, const int header_width, const int indent_width,
-  const int depth, bool parent_expanded)
+  const int depth, const bool parent_expanded)
 {
   REQUIRE(depth >= 0);
   
diff --git a/src/gui/widgets/timeline/timeline-layout-helper.hpp b/src/gui/widgets/timeline/timeline-layout-helper.hpp
index 0960afd10..08e3588be 100644
--- a/src/gui/widgets/timeline/timeline-layout-helper.hpp
+++ b/src/gui/widgets/timeline/timeline-layout-helper.hpp
@@ -99,7 +99,7 @@ protected:
   void layout_headers_recursive(
     TrackTree::iterator_base parent_iterator,
     int &offset, const int header_width, const int indent_width,
-    const int depth, bool parent_expanded);
+    const int depth, const bool parent_expanded);
   
   /**
    * A helper function which calls lookup_timeline_track within the