diff --git a/wp-admin/includes/plugin.php b/wp-admin/includes/plugin.php
index 04e7a1774e..c63ac81099 100644
--- a/wp-admin/includes/plugin.php
+++ b/wp-admin/includes/plugin.php
@@ -482,10 +482,6 @@ function activate_plugin( $plugin, $redirect = '', $network_wide = false) {
 			wp_redirect(add_query_arg('_error_nonce', wp_create_nonce('plugin-activation-error_' . $plugin), $redirect)); // we'll override this later if the plugin can be included without fatal error
 		ob_start();
 		include(WP_PLUGIN_DIR . '/' . $plugin);
-		if ( ob_get_length() > 0 ) {
-			$output = ob_get_clean();
-			return new WP_Error('unexpected_output', __('The plugin generated unexpected output.'), $output);
-		}
 		do_action( 'activate_plugin', trim( $plugin) );
 		if ( $network_wide ) {
 			$current[$plugin] = time();
@@ -497,6 +493,10 @@ function activate_plugin( $plugin, $redirect = '', $network_wide = false) {
 		}
 		do_action( 'activate_' . trim( $plugin ) );
 		do_action( 'activated_plugin', trim( $plugin) );
+		if ( ob_get_length() > 0 ) {
+			$output = ob_get_clean();
+			return new WP_Error('unexpected_output', __('The plugin generated unexpected output.'), $output);
+		}
 		ob_end_clean();
 	}
 
diff --git a/wp-admin/plugins.php b/wp-admin/plugins.php
index 155eb262ff..eff0c22fa4 100644
--- a/wp-admin/plugins.php
+++ b/wp-admin/plugins.php
@@ -334,15 +334,14 @@ if ( !empty($invalid) )
 
 <?php if ( isset($_GET['error']) ) :
 
-	if (isset($_GET['charsout']))
-		$errmsg = sprintf(__('Plugin could not be activated because it generated %d characters of <strong>unexpected output</strong>.'), $_GET['charsout']);
+	if ( isset($_GET['charsout']) )
+		$errmsg = sprintf(__('The plugin generated %d characters of <strong>unexpected output</strong> during activation.  If you notice &#8220;headers already sent&#8221; messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.'), $_GET['charsout']);
 	else
 		$errmsg = __('Plugin could not be activated because it triggered a <strong>fatal error</strong>.');
-
 	?>
 	<div id="message" class="updated"><p><?php echo $errmsg; ?></p>
 	<?php
-		if ( wp_verify_nonce($_GET['_error_nonce'], 'plugin-activation-error_' . $plugin) ) { ?>
+		if ( !isset($_GET['charsout']) && wp_verify_nonce($_GET['_error_nonce'], 'plugin-activation-error_' . $plugin) ) { ?>
 	<iframe style="border:0" width="100%" height="70px" src="<?php echo admin_url('plugins.php?action=error_scrape&amp;plugin=' . esc_attr($plugin) . '&amp;_wpnonce=' . esc_attr($_GET['_error_nonce'])); ?>"></iframe>
 	<?php
 		}