diff --git a/src/package.coffee b/src/package.coffee
index fdd89bc74..e0db21ccc 100644
--- a/src/package.coffee
+++ b/src/package.coffee
@@ -517,7 +517,7 @@ class Package
       console.error "Error deactivating package '#{@name}'", e.stack
 
     # We support then-able async promises as well as sync ones from deactivate
-    if deactivationResult?.then is 'function'
+    if typeof deactivationResult?.then is 'function'
       deactivationResult.then => @afterDeactivation()
     else
       @afterDeactivation()