diff --git a/run_project_tests.py b/run_project_tests.py
index 17e095b7a..d3da4e6c8 100755
--- a/run_project_tests.py
+++ b/run_project_tests.py
@@ -33,7 +33,7 @@ import time
 import multiprocessing
 import concurrent.futures as conc
 import re
-from run_unittests import get_fake_options, run_configure_inprocess
+from run_unittests import get_fake_options, run_configure
 
 from run_tests import get_backend_commands, get_backend_args_for_dir, Backend
 from run_tests import ensure_backend_detects_changes
@@ -327,9 +327,9 @@ def _run_test(testdir, test_build_dir, install_dir, extra_args, compiler, backen
     test_args = parse_test_args(testdir)
     gen_start = time.time()
     # Configure in-process
-    gen_command = [meson_command, '--prefix', '/usr', '--libdir', 'lib', testdir, test_build_dir]\
+    gen_args = ['--prefix', '/usr', '--libdir', 'lib', testdir, test_build_dir]\
         + flags + test_args + extra_args
-    (returncode, stdo, stde) = run_configure_inprocess(gen_command)
+    (returncode, stdo, stde) = run_configure(meson_command, gen_args)
     try:
         logfile = os.path.join(test_build_dir, 'meson-logs/meson-log.txt')
         with open(logfile, errors='ignore') as f:
diff --git a/run_tests.py b/run_tests.py
index 79c963948..4ac458cdd 100755
--- a/run_tests.py
+++ b/run_tests.py
@@ -31,6 +31,12 @@ from glob import glob
 
 Backend = Enum('Backend', 'ninja vs xcode')
 
+if 'MESON_EXE' in os.environ:
+    import shlex
+    meson_exe = shlex.split(os.environ['MESON_EXE'])
+else:
+    meson_exe = None
+
 if mesonlib.is_windows() or mesonlib.is_cygwin():
     exe_suffix = '.exe'
 else:
@@ -127,18 +133,28 @@ def get_fake_options(prefix):
 def should_run_linux_cross_tests():
     return shutil.which('arm-linux-gnueabihf-gcc-7') and not platform.machine().lower().startswith('arm')
 
-def run_configure_inprocess(commandlist):
+def run_configure_inprocess(meson_command, commandlist):
     old_stdout = sys.stdout
     sys.stdout = mystdout = StringIO()
     old_stderr = sys.stderr
     sys.stderr = mystderr = StringIO()
     try:
-        returncode = mesonmain.run(commandlist[1:], commandlist[0])
+        returncode = mesonmain.run(commandlist, meson_command)
     finally:
         sys.stdout = old_stdout
         sys.stderr = old_stderr
     return returncode, mystdout.getvalue(), mystderr.getvalue()
 
+def run_configure_external(full_command):
+    pc, o, e = mesonlib.Popen_safe(full_command)
+    return pc.returncode, o, e
+
+def run_configure(meson_command, commandlist):
+    global meson_exe
+    if meson_exe:
+        return run_configure_external(meson_exe + commandlist)
+    return run_configure_inprocess(meson_command, commandlist)
+
 class FakeEnvironment(object):
     def __init__(self):
         self.cross_info = None
diff --git a/run_unittests.py b/run_unittests.py
index 80c58ea0c..2d4dfbbe5 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -40,7 +40,7 @@ from mesonbuild.dependencies import PkgConfigDependency, ExternalProgram
 
 from run_tests import exe_suffix, get_fake_options, FakeEnvironment
 from run_tests import get_builddir_target_args, get_backend_commands, Backend
-from run_tests import ensure_backend_detects_changes, run_configure_inprocess
+from run_tests import ensure_backend_detects_changes, run_configure
 from run_tests import should_run_linux_cross_tests
 
 
@@ -460,8 +460,9 @@ class BasePlatformTests(unittest.TestCase):
         # Get the backend
         # FIXME: Extract this from argv?
         self.backend = getattr(Backend, os.environ.get('MESON_UNIT_TEST_BACKEND', 'ninja'))
-        self.meson_args = [os.path.join(src_root, 'meson.py'), '--backend=' + self.backend.name]
-        self.meson_command = [sys.executable] + self.meson_args
+        self.meson_mainfile = os.path.join(src_root, 'meson.py')
+        self.meson_args = ['--backend=' + self.backend.name]
+        self.meson_command = [sys.executable, self.meson_mainfile] + self.meson_args
         self.mconf_command = [sys.executable, os.path.join(src_root, 'meson.py'), 'configure']
         self.mintro_command = [sys.executable, os.path.join(src_root, 'meson.py'), 'introspect']
         self.mtest_command = [sys.executable, os.path.join(src_root, 'meson.py'), 'test', '-C', self.builddir]
@@ -527,7 +528,7 @@ class BasePlatformTests(unittest.TestCase):
         self.privatedir = os.path.join(self.builddir, 'meson-private')
         if inprocess:
             try:
-                out = run_configure_inprocess(self.meson_args + args + extra_args)[1]
+                out = run_configure(self.meson_mainfile, self.meson_args + args + extra_args)[1]
             except:
                 self._print_meson_log()
                 raise