diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index dce925a677..8ca5ca17de 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -4740,7 +4740,9 @@ function reset_mbstring_encoding() {
 }
 
 /**
- * Alternative to filter_var( $var, FILTER_VALIDATE_BOOLEAN ).
+ * Filter/validate a variable as a boolean.
+ *
+ * Alternative to `filter_var( $var, FILTER_VALIDATE_BOOLEAN )`.
  *
  * @since 4.0.0
  *
@@ -4752,7 +4754,7 @@ function wp_validate_boolean( $var ) {
 		return $var;
 	}
 
-	if ( 'false' === $var ) {
+	if ( is_string( $var ) && 'false' === strtolower( $var ) ) {
 		return false;
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b257e972fd..a67ccea9b2 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.1-alpha-30206';
+$wp_version = '4.1-alpha-30207';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.