diff --git a/Makefile b/Makefile
index 59dd26d..3f110fe 100644
--- a/Makefile
+++ b/Makefile
@@ -2,6 +2,7 @@ include mk/common.mk
 
 CFLAGS = \
 	-Wall -pipe -O2 \
+	-I src \
 	-I include \
 	-I backend \
 	-I apps \
diff --git a/include/twin_private.h b/src/twin_private.h
similarity index 100%
rename from include/twin_private.h
rename to src/twin_private.h