diff --git a/direct/src/interval/p3interval_composite1.cxx b/direct/src/interval/p3interval_composite1.cxx
index 6c19245712..862b622df9 100644
--- a/direct/src/interval/p3interval_composite1.cxx
+++ b/direct/src/interval/p3interval_composite1.cxx
@@ -13,3 +13,4 @@
 #include "hideInterval.cxx"
 #include "showInterval.cxx"
 #include "waitInterval.cxx"
+#include "lerpblend.cxx"