diff --git a/test/completion.js b/test/completion.js
index 7625b8e5d..4324fc5ca 100644
--- a/test/completion.js
+++ b/test/completion.js
@@ -158,6 +158,13 @@ describe('Completion', () => {
 
       r.logs[0].should.match(/\.\/test.js --get-yargs-completions/)
     })
+
+    it('allows $0 and cmd to be set', () => {
+      const r = checkUsage(() => yargs([])
+        .showCompletionScript('/path/to/my/app', 'show-completions-script'))
+
+      r.logs[0].should.match(/Installation: \/path\/to\/my\/app show-completions-script/)
+    })
   })
 
   describe('completion()', () => {
diff --git a/yargs.js b/yargs.js
index e9eae4bac..39ceb15cf 100644
--- a/yargs.js
+++ b/yargs.js
@@ -907,7 +907,7 @@ function Yargs (processArgs, cwd, parentRequire) {
     }
 
     // register the completion command.
-    completionCommand = cmd || 'completion'
+    completionCommand = cmd || completionCommand || 'completion'
     if (!desc && desc !== false) {
       desc = 'generate completion script'
     }
@@ -919,9 +919,10 @@ function Yargs (processArgs, cwd, parentRequire) {
     return self
   }
 
-  self.showCompletionScript = function ($0) {
-    argsert('[string]', [$0], arguments.length)
+  self.showCompletionScript = function ($0, cmd) {
+    argsert('[string] [string]', [$0, cmd], arguments.length)
     $0 = $0 || self.$0
+    completionCommand = cmd || completionCommand || 'completion'
     _logger.log(completion.generateCompletionScript($0, completionCommand))
     return self
   }