diff --git a/src/gfx/region.cpp b/src/gfx/region.cpp
index 54f9ecdd9..fd47585db 100644
--- a/src/gfx/region.cpp
+++ b/src/gfx/region.cpp
@@ -154,6 +154,11 @@ bool Region::contains(const PointT<int>& pt) const
 
 Region::Overlap Region::contains(const Rect& rect) const
 {
+  static_assert(
+    Out   == PIXMAN_REGION_OUT &&
+    In    == PIXMAN_REGION_IN &&
+    Part  == PIXMAN_REGION_PART, "Pixman constants have changed");
+
   pixman_box32 box = { rect.x, rect.y, rect.x2(), rect.y2() };
   return (Region::Overlap)pixman_region32_contains_rectangle(&m_region, &box);
 }