diff --git a/includes/sp-core-functions.php b/includes/sp-core-functions.php
index ce378ca0..832d01c3 100644
--- a/includes/sp-core-functions.php
+++ b/includes/sp-core-functions.php
@@ -1146,7 +1146,7 @@ if ( !function_exists( 'sp_get_eos_safe_slug' ) ) {
 }
 
 if ( !function_exists( 'sp_solve' ) ) {
-	function sp_solve( $equation, $vars, $precision = 0, $default = '-' ) {
+	function sp_solve( $equation, $vars, $precision = 0, $default = 0 ) {
 
 		if ( $equation == null )
 			return $default;