diff --git a/python/mozbuild/mozbuild/mach_commands.py b/python/mozbuild/mozbuild/mach_commands.py
index 84a8791ce60..0bdf3213883 100644
--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -765,10 +765,11 @@ class GTestCommands(MachCommandBase):
             # current OS.
             debugger = mozdebug.get_default_debugger_name(mozdebug.DebuggerSearch.KeepLooking)
 
-        debuggerInfo = mozdebug.get_debugger_info(debugger, debugger_args)
-        if not debuggerInfo:
-            print("Could not find a suitable debugger in your PATH.")
-            return 1
+        if debugger:
+            debuggerInfo = mozdebug.get_debugger_info(debugger, debugger_args)
+            if not debuggerInfo:
+                print("Could not find a suitable debugger in your PATH.")
+                return 1
 
         # Parameters come from the CLI. We need to convert them before
         # their use.
@@ -942,10 +943,11 @@ class RunProgram(MachCommandBase):
                 # current OS.
                 debugger = mozdebug.get_default_debugger_name(mozdebug.DebuggerSearch.KeepLooking)
 
-            self.debuggerInfo = mozdebug.get_debugger_info(debugger, debugparams)
-            if not self.debuggerInfo:
-                print("Could not find a suitable debugger in your PATH.")
-                return 1
+            if debugger:
+                self.debuggerInfo = mozdebug.get_debugger_info(debugger, debugparams)
+                if not self.debuggerInfo:
+                    print("Could not find a suitable debugger in your PATH.")
+                    return 1
 
             # Parameters come from the CLI. We need to convert them before
             # their use.
diff --git a/testing/mochitest/runtests.py b/testing/mochitest/runtests.py
index 82a08d9a4b7..7107b926ea7 100644
--- a/testing/mochitest/runtests.py
+++ b/testing/mochitest/runtests.py
@@ -1801,9 +1801,11 @@ class Mochitest(MochitestUtilsMixin):
     # TODO: use mozrunner.local.debugger_arguments:
     # https://github.com/mozilla/mozbase/blob/master/mozrunner/mozrunner/local.py#L42
 
-    debuggerInfo = mozdebug.get_debugger_info(options.debugger,
-                                              options.debuggerArgs,
-                                              options.debuggerInteractive)
+    debuggerInfo = None
+    if options.debugger:
+        debuggerInfo = mozdebug.get_debugger_info(options.debugger,
+                                                  options.debuggerArgs,
+                                                  options.debuggerInteractive)
 
     if options.useTestMediaDevices:
       devices = findTestMediaDevices(self.log)