diff --git a/wptrunner/browsers/b2g.py b/wptrunner/browsers/b2g.py
index e642897f158d8b..5f00feae1afd2a 100644
--- a/wptrunner/browsers/b2g.py
+++ b/wptrunner/browsers/b2g.py
@@ -42,7 +42,8 @@ def browser_kwargs(test_environment, **kwargs):
             "no_backup": kwargs.get("b2g_no_backup", False)}
 
 
-def executor_kwargs(test_type, server_config, cache_manager, **kwargs):
+def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
+                    **kwargs):
     timeout_multiplier = kwargs["timeout_multiplier"]
     if timeout_multiplier is None:
         timeout_multiplier = 2
diff --git a/wptrunner/browsers/chrome.py b/wptrunner/browsers/chrome.py
index 9b87daa4aacfc1..e766b07e95eceb 100644
--- a/wptrunner/browsers/chrome.py
+++ b/wptrunner/browsers/chrome.py
@@ -28,7 +28,8 @@ def browser_kwargs(**kwargs):
             "webdriver_binary": kwargs["webdriver_binary"]}
 
 
-def executor_kwargs(test_type, server_config, cache_manager, **kwargs):
+def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
+                    **kwargs):
     from selenium.webdriver import DesiredCapabilities
 
     executor_kwargs = base_executor_kwargs(test_type, server_config,
diff --git a/wptrunner/browsers/firefox.py b/wptrunner/browsers/firefox.py
index e0b79786969a8c..127308a7080ca0 100644
--- a/wptrunner/browsers/firefox.py
+++ b/wptrunner/browsers/firefox.py
@@ -46,10 +46,13 @@ def browser_kwargs(**kwargs):
             "ca_certificate_path": kwargs["ssl_env"].ca_cert_path()}
 
 
-def executor_kwargs(test_type, server_config, cache_manager, **kwargs):
+def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
+                    **kwargs):
     executor_kwargs = base_executor_kwargs(test_type, server_config,
                                            cache_manager, **kwargs)
     executor_kwargs["close_after_done"] = True
+    if run_info_data["debug"] and kwargs["timeout_multiplier"] is None:
+        executor_kwargs["timeout_multiplier"] = 3
     return executor_kwargs
 
 
diff --git a/wptrunner/browsers/servo.py b/wptrunner/browsers/servo.py
index 11499b66b9f42c..16f870c6937796 100644
--- a/wptrunner/browsers/servo.py
+++ b/wptrunner/browsers/servo.py
@@ -29,7 +29,8 @@ def browser_kwargs(**kwargs):
             "debug_info": kwargs["debug_info"]}
 
 
-def executor_kwargs(test_type, server_config, cache_manager, **kwargs):
+def executor_kwargs(test_type, server_config, cache_manager, run_info_data,
+                    **kwargs):
     rv = base_executor_kwargs(test_type, server_config,
                               cache_manager, **kwargs)
     rv["pause_after_test"] = kwargs["pause_after_test"]
diff --git a/wptrunner/wptcommandline.py b/wptrunner/wptcommandline.py
index bf00901ab37124..5586eb9815dd30 100644
--- a/wptrunner/wptcommandline.py
+++ b/wptrunner/wptcommandline.py
@@ -86,6 +86,14 @@ def create_parser(product_choices=None):
                         default=False,
                         help="List the tests that are disabled on the current platform")
 
+    build_type = parser.add_mutually_exclusive_group()
+    build_type.add_argument("--debug-build", dest="debug", action="store_true",
+                            default=None,
+                            help="Build is a debug build (overrides any mozinfo file)")
+    build_type.add_argument("--release-build", dest="debug", action="store_false",
+                            default=None,
+                            help="Build is a release (overrides any mozinfo file)")
+
     test_selection_group = parser.add_argument_group("Test Selection")
     test_selection_group.add_argument("--test-types", action="store",
                                       nargs="*", default=["testharness", "reftest"],
diff --git a/wptrunner/wptrunner.py b/wptrunner/wptrunner.py
index 075f07cdc0dbb5..502da490cb567e 100644
--- a/wptrunner/wptrunner.py
+++ b/wptrunner/wptrunner.py
@@ -40,7 +40,7 @@ def setup_logging(*args, **kwargs):
     global logger
     logger = wptlogging.setup(*args, **kwargs)
 
-def get_loader(test_paths, product, ssl_env, debug=False, **kwargs):
+def get_loader(test_paths, product, ssl_env, debug=None, **kwargs):
     run_info = wpttest.get_run_info(kwargs["run_info"], product, debug=debug)
 
     test_manifests = testloader.ManifestLoader(test_paths, force_manifest_update=kwargs["manifest_update"]).load()
@@ -111,7 +111,7 @@ def run_tests(config, test_paths, product, **kwargs):
         check_args(**kwargs)
 
         if "test_loader" in kwargs:
-            run_info = wpttest.get_run_info(kwargs["run_info"], product, debug=False)
+            run_info = wpttest.get_run_info(kwargs["run_info"], product, debug=None)
             test_loader = kwargs["test_loader"]
         else:
             run_info, test_loader = get_loader(test_paths, product, ssl_env,
@@ -163,6 +163,7 @@ def run_tests(config, test_paths, product, **kwargs):
                     executor_kwargs = get_executor_kwargs(test_type,
                                                           test_environment.external_config,
                                                           test_environment.cache_manager,
+                                                          run_info,
                                                           **kwargs)
 
                     if executor_cls is None:
diff --git a/wptrunner/wpttest.py b/wptrunner/wpttest.py
index d2d19fe5489bbd..c5b8ae1f1d4823 100644
--- a/wptrunner/wpttest.py
+++ b/wptrunner/wpttest.py
@@ -58,8 +58,11 @@ def __init__(self, metadata_root, product, debug):
         self._update_mozinfo(metadata_root)
         self.update(mozinfo.info)
         self["product"] = product
-        if not "debug" in self:
+        if debug is not None:
             self["debug"] = debug
+        elif "debug" not in self:
+            # Default to release
+            self["debug"] = False
 
     def _update_mozinfo(self, metadata_root):
         """Add extra build information from a mozinfo.json file in a parent