--- a/mozharness/mozilla/purge.py
+++ b/mozharness/mozilla/purge.py
@@ -116,16 +116,19 @@ class PurgeMixin(object):
                          'error_list':error_list})
         if retval != 0:
             self.fatal("failed to clobber build", exit_code=2)
 
     def clobber(self, always_clobber_dirs=None):
         """ Mozilla clobberer-type clobber.
             """
         c = self.config
+        if c.get('developer_mode'):
+            self.info("Suppressing clobber in developer mode for safety.")
+            return
         if c.get('is_automation'):
             # Nightly builds always clobber
             do_clobber = False
             if self.query_is_nightly():
                 self.info("Clobbering because we're a nightly build")
                 do_clobber = True
             if c.get('force_clobber'):
                 self.info("Clobbering because our config forced us to")