diff --git a/includes/math-expr.inc b/includes/math-expr.inc
index 4b13a67..1e18038 100644
--- a/includes/math-expr.inc
+++ b/includes/math-expr.inc
@@ -178,8 +178,8 @@ class ctools_math_expr {
   /**
    * Backwards compatible wrapper for evaluate().
    */
-  function e($expr) {
-    return evaluate($expr);
+  public function e($expr) {
+    return $this->evaluate($expr);
   }
 
   /**
@@ -188,7 +188,7 @@ class ctools_math_expr {
    * @param string $expr The expression to evaluate.
    * @return string
    */
-  function evaluate($expr) {
+  public function evaluate($expr) {
     $this->last_error = NULL;
     $expr = trim($expr);
     if (substr($expr, -1, 1) == ';') {
@@ -471,7 +471,7 @@ class ctools_math_expr {
   }
 
   // evaluate postfix notation
-  function pfx($tokens, $vars = array()) {
+  public function pfx($tokens, $vars = array()) {
 
     if ($tokens == FALSE) {
       return FALSE;
@@ -590,7 +590,7 @@ class ctools_math_expr {
   }
 
   // trigger an error, but nicely, if need be
-  function trigger($msg) {
+  protected function trigger($msg) {
     $this->errors[] = $msg;
     $this->last_error = $msg;
     if (!$this->suppress_errors) {