diff --git a/tests/test_plot/test_misc.py b/tests/test_plot/test_misc.py
index a88b4d58..476d0ea8 100644
--- a/tests/test_plot/test_misc.py
+++ b/tests/test_plot/test_misc.py
@@ -600,7 +600,7 @@ def check_test_v5_sch_deps(ctx, deps, extra=[], in_output=False):
 
 def check_makefile(ctx, mkfile, prj, dbg, txt):
     ctx.expect_out_file('Makefile')
-    res = ctx.search_in_file('Makefile', ['DEBUG=(.*)', txt])
+    res = ctx.search_in_file('Makefile', [r'DEBUG\?=(.*)', txt])
     assert res[0][0] == dbg, res
     targets = ctx.read_mk_targets(mkfile)
     all = targets['all']
diff --git a/tests/test_plot/test_misc_2.py b/tests/test_plot/test_misc_2.py
index b2203f98..311ef79c 100644
--- a/tests/test_plot/test_misc_2.py
+++ b/tests/test_plot/test_misc_2.py
@@ -326,5 +326,5 @@ def test_makefile_kibot_sys(test_dir):
     GS.out_dir = ctx.get_out_path('')
     with context.cover_it(cov):
         generate_makefile(ctx.get_out_path('Makefile'), 'pp', [], kibot_sys=True)
-    ctx.search_in_file('Makefile', ['KIBOT=kibot'])
+    ctx.search_in_file('Makefile', [r'KIBOT\?=kibot'])
     ctx.clean_up()