diff --git a/wp-includes/meta.php b/wp-includes/meta.php
index 4066781af0..357c12c112 100644
--- a/wp-includes/meta.php
+++ b/wp-includes/meta.php
@@ -753,7 +753,7 @@ class WP_Meta_Query {
 		// Split out the meta_key only queries (we can only do this for OR)
 		if ( 'OR' == $this->relation ) {
 			foreach ( $this->queries as $k => $q ) {
-				if ( ! isset( $q['value'] ) && ! empty( $q['key'] ) )
+				if ( ! array_key_exists( 'value', $q ) && ! empty( $q['key'] ) )
 					$key_only_queries[$k] = $q;
 				else
 					$queries[$k] = $q;
@@ -774,6 +774,9 @@ class WP_Meta_Query {
 			$meta_key = isset( $q['key'] ) ? trim( $q['key'] ) : '';
 			$meta_type = $this->get_cast_for_type( isset( $q['type'] ) ? $q['type'] : '' );
 
+			if ( array_key_exists( 'value', $q ) && is_null( $q['value'] ) )
+				$q['value'] = '';
+
 			$meta_value = isset( $q['value'] ) ? $q['value'] : null;
 
 			if ( isset( $q['compare'] ) )