diff --git a/Readme.md b/Readme.md
index ebbe86f9..05ae44fe 100644
--- a/Readme.md
+++ b/Readme.md
@@ -156,6 +156,7 @@ Here are a few notable options.
  - [Benchmark/Test] Disable threading/forking with `in_threads: 0` or `in_processes: 0`, great to test performance or to debug parallel issues
  - [Isolation] Do not reuse previous worker processes: `isolation: true`
  - [Stop all processses with an alternate interrupt signal] `'INT'` (from `ctrl+c`) is caught by default. Catch `'TERM'` (from `kill`) with `interrupt_signal: 'TERM'`
+ - You can set the environment variable `PARALLEL_OVERRIDE_PROCESSOR_COUNT` to use a custom default value of procesess / threads instead of the number of processors detected.
 
 TODO
 ====
diff --git a/lib/parallel/processor_count.rb b/lib/parallel/processor_count.rb
index 9ba65249..a929ab5d 100644
--- a/lib/parallel/processor_count.rb
+++ b/lib/parallel/processor_count.rb
@@ -5,7 +5,7 @@ module ProcessorCount
     # Number of processors seen by the OS and used for process scheduling. It's just wrapper for Etc.nprocessors
     def processor_count
       @processor_count ||= begin
-        Etc.nprocessors
+        (ENV['PARALLEL_OVERRIDE_PROCESSOR_COUNT'] || Etc.nprocessors).to_i
       end
     end