diff --git a/Makefile.am b/Makefile.am
index 37cfe61b..d79637df 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -61,6 +61,8 @@ if ENABLE_UBSAN
 AM_CFLAGS += -fsanitize=undefined
 endif
 
+AM_CPPFLAGS = -I$(srcdir)/src
+
 ### Running tests under Valgrind
 
 if ENABLE_ASAN