diff --git a/tests/Makefile.am b/tests/Makefile.am
index 378d4d3..4f18f34 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -41,7 +41,8 @@ AM_CPPFLAGS = \
     -include $(top_builddir)/config.h \
     -DSYSCONFDIR=\""$(sysconfdir)"\" \
     -DLIBEXECDIR=\""$(libexecdir)"\" \
-    -I${top_srcdir}/src
+    -I${top_srcdir}/src \
+    -I${top_builddir}/src
 
 AM_CFLAGS = ${my_CFLAGS}