diff --git a/python/mozbuild/mozbuild/mach_commands.py b/python/mozbuild/mozbuild/mach_commands.py
index 3e3bb3064cb8..89156ff47a1b 100644
--- a/python/mozbuild/mozbuild/mach_commands.py
+++ b/python/mozbuild/mozbuild/mach_commands.py
@@ -4,6 +4,7 @@
 
 from __future__ import print_function, unicode_literals
 
+import getpass
 import logging
 import operator
 import os
@@ -189,6 +190,9 @@ class Build(MachCommandBase):
             if proc.name != 'Finder':
                 continue
 
+            if proc.username != getpass.getuser():
+                continue
+
             # Try to isolate system finder as opposed to other "Finder"
             # processes.
             if not proc.exe.endswith('CoreServices/Finder.app/Contents/MacOS/Finder'):