diff --git a/bin/run-superuser-tests b/bin/run-superuser-tests
index 141e966..a6e6484 100755
--- a/bin/run-superuser-tests
+++ b/bin/run-superuser-tests
@@ -2,10 +2,11 @@
 set -e
 if [ $(id -u) = 0 ]; then
     rake clean clobber compile
+    rm -rf tmp/
     for file in test/superuser/*_test.rb; do
         ruby -Ilib ${file} --no-use-color
     done
 else
-    echo "You must be root to run superuser tests."
+    echo "You must be the root user to run these tests."
     exit 1
 fi
diff --git a/bin/run-unprivileged-tests b/bin/run-unprivileged-tests
index 24ad22b..852965e 100755
--- a/bin/run-unprivileged-tests
+++ b/bin/run-unprivileged-tests
@@ -1,6 +1,11 @@
 #!/bin/sh
 set -e
-rake clean clobber compile
-for file in test/unprivileged/*_test.rb; do
-    ruby -Ilib ${file} --no-use-color
-done
+if [ $(id -u) -ne 0 ]; then
+    rake clean clobber compile
+    for file in test/unprivileged/*_test.rb; do
+        ruby -Ilib ${file} --no-use-color
+    done
+else
+    echo "You must be an unprivileged user to run these tests."
+    exit 1
+fi
diff --git a/test/superuser/enable_feature_test.rb b/test/superuser/enable_feature_test.rb
index c146818..53a4d7f 100644
--- a/test/superuser/enable_feature_test.rb
+++ b/test/superuser/enable_feature_test.rb
@@ -12,6 +12,15 @@ module BSD::Control
       rm(file)
     end
 
+    def test_enable_mprotect_zero_permissions
+      touch(file)
+      chmod(0, file)
+      assert BSD::Control.feature!(:mprotect).enable!(file),
+             "The enable! method should have returned true"
+    ensure
+      rm(file)
+    end
+
     def test_enable_mprotect_nonexistent_file
       assert_raises(BSD::Control::Error) do
         BSD::Control.feature!(:mprotect).enable!(file)
diff --git a/test/unprivileged/enable_feature_test.rb b/test/unprivileged/enable_feature_test.rb
new file mode 100644
index 0000000..1ad434a
--- /dev/null
+++ b/test/unprivileged/enable_feature_test.rb
@@ -0,0 +1,25 @@
+require_relative "../setup"
+module BSD::Control
+  class EnableFeatureTest < Test::Unit::TestCase
+    require "fileutils"
+    include FileUtils
+
+    def test_enable_feature_lacks_privileges
+      touch(file)
+      assert_raises(
+        BSD::Control::Error,
+        "This operation requires root privileges."
+      ) do
+        BSD::Control.feature!(:mprotect).enable!(file)
+      end
+    ensure
+      rm(file)
+    end
+
+    private
+
+    def file
+      File.join(__dir__, "file")
+    end
+  end
+end