diff --git a/wp-includes/bookmark.php b/wp-includes/bookmark.php
index 1f85c9cfc5..9e6f0d360a 100644
--- a/wp-includes/bookmark.php
+++ b/wp-includes/bookmark.php
@@ -136,7 +136,7 @@ function get_bookmarks($args = '') {
 	$results = $wpdb->get_results($query);
 
 	$cache[ $key ] = $results;
-	wp_cache_set( 'get_bookmarks', $cache, 'bookmark' );
+	wp_cache_add( 'get_bookmarks', $cache, 'bookmark' );
 
 	return apply_filters('get_bookmarks', $results, $r);
 }
diff --git a/wp-includes/category.php b/wp-includes/category.php
index 7de7c81dd8..b60fd238e7 100644
--- a/wp-includes/category.php
+++ b/wp-includes/category.php
@@ -8,7 +8,7 @@ function get_all_category_ids() {
 
 	if ( ! $cat_ids = wp_cache_get('all_category_ids', 'category') ) {
 		$cat_ids = $wpdb->get_col("SELECT cat_ID FROM $wpdb->categories");
-		wp_cache_set('all_category_ids', $cat_ids, 'category');
+		wp_cache_add('all_category_ids', $cat_ids, 'category');
 	}
 
 	return $cat_ids;
@@ -139,7 +139,7 @@ function &get_categories($args = '') {
 	reset ( $categories );
 
 	$cache[ $key ] = $categories;
-	wp_cache_set( 'get_categories', $cache, 'category' );
+	wp_cache_add( 'get_categories', $cache, 'category' );
 
 	$categories = apply_filters('get_categories', $categories, $r);
 	return $categories;
@@ -160,7 +160,7 @@ function &get_category(&$category, $output = OBJECT) {
 		$category = (int) $category;
 		if ( ! $_category = wp_cache_get($category, 'category') ) {
 			$_category = $wpdb->get_row("SELECT * FROM $wpdb->categories WHERE cat_ID = '$category' LIMIT 1");
-			wp_cache_set($category, $_category, 'category');
+			wp_cache_add($category, $_category, 'category');
 		}
 	}
 
diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 8ca5e2742c..d7b2a1ae8d 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -229,7 +229,7 @@ function get_option($setting) {
 
 			if( is_object( $row) ) { // Has to be get_row instead of get_var because of funkiness with 0, false, null values
 				$value = $row->option_value;
-				wp_cache_set($setting, $value, 'options');
+				wp_cache_add($setting, $value, 'options');
 			} else { // option does not exist, so we must cache its non-existence
 				$notoptions[$setting] = true;
 				wp_cache_set('notoptions', $notoptions, 'options');
@@ -294,7 +294,7 @@ function wp_load_alloptions() {
 		$alloptions = array();
 		foreach ( (array) $alloptions_db as $o )
 			$alloptions[$o->option_name] = $o->option_value;
-		wp_cache_set('alloptions', $alloptions, 'options');
+		wp_cache_add('alloptions', $alloptions, 'options');
 	}
 	return $alloptions;
 }
diff --git a/wp-includes/general-template.php b/wp-includes/general-template.php
index 7b08d99ab7..bf8f275037 100644
--- a/wp-includes/general-template.php
+++ b/wp-includes/general-template.php
@@ -635,7 +635,7 @@ function get_calendar($initial = true) {
 	ob_end_clean();
 	echo $output;
 	$cache[ $key ] = $output;
-	wp_cache_set( 'get_calendar', $cache, 'calendar' );
+	wp_cache_add( 'get_calendar', $cache, 'calendar' );
 }
 
 function delete_get_calendar_cache() {
diff --git a/wp-includes/post.php b/wp-includes/post.php
index fa08e89ae3..ac0a0fa704 100644
--- a/wp-includes/post.php
+++ b/wp-includes/post.php
@@ -1012,7 +1012,7 @@ function get_all_page_ids() {
 
 	if ( ! $page_ids = wp_cache_get('all_page_ids', 'pages') ) {
 		$page_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE post_type = 'page'");
-		wp_cache_set('all_page_ids', $page_ids, 'pages');
+		wp_cache_add('all_page_ids', $page_ids, 'pages');
 	}
 
 	return $page_ids;
@@ -1055,7 +1055,7 @@ function &get_page(&$page, $output = OBJECT) {
 					return get_post($_page, $output);
 				// Potential issue: we're not checking to see if the post_type = 'page'
 				// So all non-'post' posts will get cached as pages.
-				wp_cache_set($_page->ID, $_page, 'pages');
+				wp_cache_add($_page->ID, $_page, 'pages');
 			}
 		}
 	}