diff --git a/Makefile.am b/Makefile.am
index 5299a8332e..4a0307323f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2691,12 +2691,13 @@ check_programs += src/core/initrd/tests/test-dt-reader
 
 src_core_initrd_tests_test_dt_reader_CPPFLAGS = \
 	-DNETWORKMANAGER_COMPILATION_TEST \
-	-DTEST_INITRD_DIR=\"$(abs_srcdir)/src/core/initrd/tests\" \
-	$(src_core_cppflags)
+	$(src_core_cppflags) \
+	$(NULL)
 
 src_core_initrd_tests_test_dt_reader_LDFLAGS = \
 	$(CODE_COVERAGE_LDFLAGS) \
-	$(SANITIZER_EXEC_LDFLAGS)
+	$(SANITIZER_EXEC_LDFLAGS) \
+	$(NULL)
 
 src_core_initrd_tests_test_dt_reader_LDADD = \
 	src/core/initrd/libnmi-core.la \
@@ -2711,12 +2712,13 @@ check_programs += src/core/initrd/tests/test-ibft-reader
 
 src_core_initrd_tests_test_ibft_reader_CPPFLAGS = \
 	-DNETWORKMANAGER_COMPILATION_TEST \
-	-DTEST_INITRD_DIR=\"$(abs_srcdir)/src/core/initrd/tests\" \
-	$(src_core_cppflags)
+	$(src_core_cppflags) \
+	$(NULL)
 
 src_core_initrd_tests_test_ibft_reader_LDFLAGS = \
 	$(CODE_COVERAGE_LDFLAGS) \
-	$(SANITIZER_EXEC_LDFLAGS)
+	$(SANITIZER_EXEC_LDFLAGS) \
+	$(NULL)
 
 src_core_initrd_tests_test_ibft_reader_LDADD = \
 	src/core/initrd/libnmi-core.la \
@@ -2947,8 +2949,8 @@ check_programs += src/core/initrd/tests/test-cmdline-reader
 
 src_core_initrd_tests_test_cmdline_reader_CPPFLAGS = \
 	-DNETWORKMANAGER_COMPILATION_TEST \
-	-DTEST_INITRD_DIR=\"$(abs_srcdir)/src/core/initrd/tests\" \
-	$(src_core_cppflags)
+	$(src_core_cppflags) \
+	$(NULL)
 
 src_core_initrd_tests_test_cmdline_reader_LDFLAGS = \
 	$(CODE_COVERAGE_LDFLAGS) \
diff --git a/src/core/initrd/tests/meson.build b/src/core/initrd/tests/meson.build
index 51650d0f15..e47ff7905d 100644
--- a/src/core/initrd/tests/meson.build
+++ b/src/core/initrd/tests/meson.build
@@ -1,7 +1,5 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
-c_flags = test_c_flags + ['-DTEST_INITRD_DIR="@0@"'.format(meson.current_source_dir())]
-
 test_units = [
   'test-dt-reader',
   'test-ibft-reader',
@@ -13,7 +11,7 @@ foreach test_unit : test_units
     test_unit,
     test_unit + '.c',
     dependencies: libNetworkManagerTest_dep,
-    c_args: c_flags,
+    c_args: test_c_flags,
     link_with: libnmi_core,
   )
 
diff --git a/src/core/initrd/tests/test-cmdline-reader.c b/src/core/initrd/tests/test-cmdline-reader.c
index 1dc0988e38..7b8c2b0d0b 100644
--- a/src/core/initrd/tests/test-cmdline-reader.c
+++ b/src/core/initrd/tests/test-cmdline-reader.c
@@ -19,6 +19,8 @@
 
 #include "nm-test-utils-core.h"
 
+#define TEST_INITRD_DIR NM_BUILD_SRCDIR "/src/core/initrd/tests"
+
 /*****************************************************************************/
 
 #define _parse(ARGV, out_hostname, out_carrier_timeout_sec)                            \
diff --git a/src/core/initrd/tests/test-dt-reader.c b/src/core/initrd/tests/test-dt-reader.c
index 982ccc3ac2..5e87d952fd 100644
--- a/src/core/initrd/tests/test-dt-reader.c
+++ b/src/core/initrd/tests/test-dt-reader.c
@@ -19,6 +19,10 @@
 
 #include "nm-test-utils-core.h"
 
+#define TEST_INITRD_DIR NM_BUILD_SRCDIR "/src/core/initrd/tests"
+
+/*****************************************************************************/
+
 static void
 test_read_dt_ofw(void)
 {
diff --git a/src/core/initrd/tests/test-ibft-reader.c b/src/core/initrd/tests/test-ibft-reader.c
index 320153f81c..3e59fe85de 100644
--- a/src/core/initrd/tests/test-ibft-reader.c
+++ b/src/core/initrd/tests/test-ibft-reader.c
@@ -19,6 +19,10 @@
 
 #include "nm-test-utils-core.h"
 
+#define TEST_INITRD_DIR NM_BUILD_SRCDIR "/src/core/initrd/tests"
+
+/*****************************************************************************/
+
 static NMConnection *
 read_connection(const char *sysfs_dir, const char *expected_mac, GError **error)
 {