diff --git a/meson.build b/meson.build
index c22e92626..52e829ac0 100644
--- a/meson.build
+++ b/meson.build
@@ -144,13 +144,14 @@ deps = []
 
 conf = configuration_data()
 incconfig = include_directories('.')
-cpp_args = ['-DHAVE_CONFIG_H']
+
+add_project_arguments('-DHAVE_CONFIG_H', language: ['c', 'cpp'])
 
 warn_cflags = [
   '-Wno-non-virtual-dtor',
 ]
 
-cpp_args += cpp.get_supported_arguments(warn_cflags)
+cpp_args = cpp.get_supported_arguments(warn_cflags)
 
 if m_dep.found()
   deps += [m_dep]
diff --git a/test/api/meson.build b/test/api/meson.build
index 0a9ade6ea..6258915bb 100644
--- a/test/api/meson.build
+++ b/test/api/meson.build
@@ -45,10 +45,9 @@ if conf.get('HAVE_GLIB', 0) == 1
     opts = test_data.length() > 1 ? test_data[1] : {}
     extra_c_args = opts.get('c_args', [])
 
-
-
     test_name = fname.split('.')[0].underscorify()
     exe = executable(test_name, fname,
+      c_args: extra_c_args,
       cpp_args: cpp_args + extra_c_args,
       include_directories: [incconfig, incsrc],
       dependencies: deps,