diff --git a/headers/libs/alm/ALMLayout.h b/headers/libs/alm/ALMLayout.h
index 98522b8698..3a691c1454 100644
--- a/headers/libs/alm/ALMLayout.h
+++ b/headers/libs/alm/ALMLayout.h
@@ -16,7 +16,11 @@
 
 class BView;
 class BLayoutItem;
-class Constraint;
+
+
+namespace LinearProgramming {
+	class Constraint;
+};
 
 
 namespace BPrivate {