diff --git a/src/NXP/Classes/Calculator.php b/src/NXP/Classes/Calculator.php
index 41e0d9f..b584d69 100644
--- a/src/NXP/Classes/Calculator.php
+++ b/src/NXP/Classes/Calculator.php
@@ -40,7 +40,7 @@ class Calculator
             if ($token instanceof TokenVariable) {
                 $variable = $token->getValue();
                 if (!array_key_exists($variable, $variables)) {
-                    throw new UnknownVariableException();
+                    throw new UnknownVariableException($variable);
                 }
                 $value = $variables[$variable];
                 array_push($stack, new TokenNumber($value));
diff --git a/src/NXP/Classes/TokenFactory.php b/src/NXP/Classes/TokenFactory.php
index 2b1e00e..85c4a62 100644
--- a/src/NXP/Classes/TokenFactory.php
+++ b/src/NXP/Classes/TokenFactory.php
@@ -73,7 +73,7 @@ class TokenFactory
         $class = new \ReflectionClass($operatorClass);
 
         if (!in_array('NXP\Classes\Token\InterfaceToken', $class->getInterfaceNames())) {
-            throw new UnknownOperatorException;
+            throw new UnknownOperatorException($operatorClass);
         }
 
         $this->operators[] = $operatorClass;
@@ -162,10 +162,10 @@ class TokenFactory
             if (isset($this->functions[$token])) {
                 return new TokenFunction($this->functions[$token]);
             } else {
-                throw new UnknownFunctionException();
+                throw new UnknownFunctionException($token);
             }
         }
 
-        throw new UnknownTokenException();
+        throw new UnknownTokenException($token);
     }
 }
diff --git a/src/NXP/MathExecutor.php b/src/NXP/MathExecutor.php
index 9e7ce25..c5c7add 100644
--- a/src/NXP/MathExecutor.php
+++ b/src/NXP/MathExecutor.php
@@ -91,6 +91,10 @@ class MathExecutor
      */
     public function setVar($variable, $value)
     {
+        if (!is_numeric($value)) {
+            throw new \Exception("Variable ({$variable}) value must be a number ({$value}) type ({gettype($value)})");
+        }
+
         $this->variables[$variable] = $value;
 
         return $this;