diff --git a/lib/get_process_mem.rb b/lib/get_process_mem.rb
index 762fae0..67aaf25 100644
--- a/lib/get_process_mem.rb
+++ b/lib/get_process_mem.rb
@@ -120,5 +120,7 @@ def ps_memory
 
   def darwin_memory
     Darwin.resident_size(pid)
+  rescue Errno::EPERM
+    nil
   end
 end