diff --git a/test/acceptance/base.rb b/test/acceptance/base.rb
index edb33cd6f..a999dbb9f 100644
--- a/test/acceptance/base.rb
+++ b/test/acceptance/base.rb
@@ -13,6 +13,10 @@ require "support/config"
 require "support/virtualbox"
 require "support/matchers/match_output"
 
+# Do not buffer output
+$stdout.sync = true
+$stderr.sync = true
+
 # If VirtualBox is currently running, fail.
 if Acceptance::VirtualBox.find_vboxsvc
   $stderr.puts "VirtualBox must be closed and remain closed for the duration of the tests."
diff --git a/test/unit/test_helper.rb b/test/unit/test_helper.rb
index fcfdaf9d5..f6a20c9b1 100644
--- a/test/unit/test_helper.rb
+++ b/test/unit/test_helper.rb
@@ -13,6 +13,10 @@ begin
 rescue LoadError
 end
 
+# Do not buffer output for tests
+$stdout.sync = true
+$stderr.sync = true
+
 # Set the home directory to some temporary directory
 ENV["HOME"] = Vagrant.source_root.join("test", "tmp", "home").to_s