diff --git a/Makefile.am b/Makefile.am
index d1f2f8a7..66d95578 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -286,7 +286,7 @@ endif
 
 TESTS = tests/unittests/unittests
 check_PROGRAMS = tests/unittests/unittests
-tests_unittests_unittests_CPPFLAGS = -Itests/
+tests_unittests_unittests_CPPFLAGS = -I$(srcdir)/tests
 tests_unittests_unittests_SOURCES = $(unittest_sources)
 tests_unittests_unittests_LDADD = -lcmocka
 
@@ -302,7 +302,7 @@ if HAVE_FORKPTY
 TESTS += tests/functionaltests/functionaltests
 check_PROGRAMS += tests/functionaltests/functionaltests
 tests_functionaltests_functionaltests_SOURCES = $(functionaltest_sources)
-tests_functionaltests_functionaltests_CPPFLAGS = -Itests/
+tests_functionaltests_functionaltests_CPPFLAGS = -I$(srcdir)/tests
 tests_functionaltests_functionaltests_CFLAGS = $(AM_CFLAGS)
 tests_functionaltests_functionaltests_LDADD = -lcmocka -lstabber @FORKPTY_LIB@