--- a/testing/marionette/client/marionette/emulator.py
+++ b/testing/marionette/client/marionette/emulator.py
@@ -382,38 +382,39 @@ waitFor(
         # gecko in order to avoid an adb bug in which adb will sometimes
         # hang indefinitely while copying large files to the system
         # partition.
         push_attempts = 10
 
         print 'installing gecko binaries...'
         # need to remount so we can write to /system/b2g
         self._run_adb(['remount'])
+        self.dm.shellCheckOutput(['stop', 'b2g'])
+        # ensure the b2g process has fully stopped (bug 809437)
+        for i in range(0, 10):
+            time.sleep(1)
+            if self.dm.processExist('b2g') is None:
+                break
+        else:
+            raise TimeoutException("Timeout waiting for the b2g process to terminate")
+
         for root, dirs, files in os.walk(gecko_path):
             for filename in files:
                 rel_path = os.path.relpath(os.path.join(root, filename), gecko_path)
                 system_b2g_file = os.path.join('/system/b2g', rel_path)
                 for retry in range(1, push_attempts+1):
                     print 'pushing', system_b2g_file, '(attempt %s of %s)' % (retry, push_attempts)
                     try:
                         self.dm.pushFile(os.path.join(root, filename), system_b2g_file)
                         break
                     except DMError:
                         if retry == push_attempts:
                             raise
 
         print 'restarting B2G'
-        self.dm.shellCheckOutput(['stop', 'b2g'])
-        # ensure the b2g process has fully stopped (bug 809437)
-        for i in range(0, 10):
-            time.sleep(1)
-            if self.dm.processExist('b2g') is None:
-                break
-        else:
-            raise TimeoutException("Timeout waiting for the b2g process to terminate")
         self.dm.shellCheckOutput(['start', 'b2g'])
 
         if not self.wait_for_port():
             raise TimeoutException("Timeout waiting for marionette on port '%s'" % self.marionette_port)
         self.wait_for_system_message(marionette)
 
     def rotate_log(self, srclog, index=1):
         """ Rotate a logfile, by recursively rotating logs further in the sequence,