--- a/toolkit/mozapps/extensions/internal/XPIProvider.jsm
+++ b/toolkit/mozapps/extensions/internal/XPIProvider.jsm
@@ -3247,18 +3247,17 @@ this.XPIProvider = {
           logger.error("Unable to read add-on manifest from " + stageDirEntry.path, e);
           // This add-on can't be installed so just remove it now
           seenFiles.push(stageDirEntry.leafName);
           seenFiles.push(jsonfile.leafName);
           continue;
         }
 
         if (mustSign(addon.type) &&
-            (addon.signedState <= AddonManager.SIGNEDSTATE_MISSING ||
-            (foreignInstall && addon.signedState < AddonManager.SIGNEDSTATE_SIGNED))) {
+            addon.signedState <= AddonManager.SIGNEDSTATE_MISSING) {
           logger.warn("Refusing to install staged add-on " + id + " with signed state " + addon.signedState);
           seenFiles.push(stageDirEntry.leafName);
           seenFiles.push(jsonfile.leafName);
           continue;
         }
 
         // Check for a cached metadata for this add-on, it may contain updated
         // compatibility information

--- a/toolkit/mozapps/extensions/test/xpcshell/test_signed_inject.js
+++ b/toolkit/mozapps/extensions/test/xpcshell/test_signed_inject.js
@@ -337,43 +337,46 @@ add_task(function*() {
 });
 
 // Preliminarily-signed sideloaded add-ons should work
 add_task(function*() {
   let file = manuallyInstall(do_get_file(DATA + ADDONS.bootstrap.preliminary), profileDir, ID);
 
   startupManager();
 
-  // Currently we leave the sideloaded add-on there but just don't run it
   let addon = yield promiseAddonByID(ID);
   do_check_neq(addon, null);
   do_check_false(addon.appDisabled);
   do_check_true(addon.isActive);
   do_check_eq(addon.signedState, AddonManager.SIGNEDSTATE_PRELIMINARY);
   do_check_eq(getActiveVersion(), 2);
 
   addon.uninstall();
   yield promiseShutdownManager();
   resetPrefs();
 
   do_check_false(file.exists());
   clearCache(file);
 });
 
+// Preliminarily-signed sideloaded add-ons should work via staged install
 add_task(function*() {
   let stage = profileDir.clone();
   stage.append("staged");
 
   let file = manuallyInstall(do_get_file(DATA + ADDONS.bootstrap.preliminary), stage, ID);
 
   startupManager();
 
-  // Should have refused to install preliminarily signed version
   let addon = yield promiseAddonByID(ID);
-  do_check_eq(addon, null);
-  do_check_eq(getActiveVersion(), -1);
+  do_check_neq(addon, null);
+  do_check_false(addon.appDisabled);
+  do_check_true(addon.isActive);
+  do_check_eq(addon.signedState, AddonManager.SIGNEDSTATE_PRELIMINARY);
+  do_check_eq(getActiveVersion(), 2);
+
+  addon.uninstall();
+  yield promiseShutdownManager();
+  resetPrefs();
 
   do_check_false(file.exists());
   clearCache(file);
-
-  yield promiseShutdownManager();
-  resetPrefs();
 });