diff --git a/src/main/java/net/objecthunter/exp4j/Expression.java b/src/main/java/net/objecthunter/exp4j/Expression.java
index 45889319..e1b1aa5d 100644
--- a/src/main/java/net/objecthunter/exp4j/Expression.java
+++ b/src/main/java/net/objecthunter/exp4j/Expression.java
@@ -97,9 +97,9 @@ public Expression setVariables(Map<String, Double> variables) {
         return this;
     }
 
-    public Set<String> getVariableTokenNames() {
-        Set<String> variables = new TreeSet<String>();
-        for (Token t: tokens) {
+    public Set<String> getVariableNames() {
+        final Set<String> variables = new HashSet<String>();
+        for (final Token t: tokens) {
             if (t.getType() == Token.TOKEN_VARIABLE)
                 variables.add(((VariableToken)t).getName());
         }
diff --git a/src/test/java/net/objecthunter/exp4j/ExpressionBuilderTest.java b/src/test/java/net/objecthunter/exp4j/ExpressionBuilderTest.java
index 6489a37d..f841af9c 100644
--- a/src/test/java/net/objecthunter/exp4j/ExpressionBuilderTest.java
+++ b/src/test/java/net/objecthunter/exp4j/ExpressionBuilderTest.java
@@ -19,9 +19,9 @@
 import static java.lang.Math.*;
 import static org.junit.Assert.*;
 
-import java.util.Date;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
@@ -2652,6 +2652,28 @@ public double apply(double... args) {
         assertEquals(expected, result, 0d);
     }
 
+    @Test
+    public void testGetVariableNames1() throws Exception{
+        Expression e = new ExpressionBuilder("b*a-9.24c")
+                .variables("b", "a", "c")
+                .build();
+        Set<String> variableNames = e.getVariableNames();
+        assertTrue(variableNames.contains("a"));
+        assertTrue(variableNames.contains("b"));
+        assertTrue(variableNames.contains("c"));
+    }
+
+    @Test
+    public void testGetVariableNames2() throws Exception{
+        Expression e = new ExpressionBuilder("log(bar)-FOO.s/9.24c")
+                .variables("bar", "FOO.s", "c")
+                .build();
+        Set<String> variableNames = e.getVariableNames();
+        assertTrue(variableNames.contains("bar"));
+        assertTrue(variableNames.contains("FOO.s"));
+        assertTrue(variableNames.contains("c"));
+    }
+
     @Test(expected = IllegalArgumentException.class)
     public void testSameVariableAndBuiltinFunctionName() {
         Expression e = new ExpressionBuilder("log10(log10)")
diff --git a/src/test/java/net/objecthunter/exp4j/ExpressionTest.java b/src/test/java/net/objecthunter/exp4j/ExpressionTest.java
index 323c43e0..50c5bd44 100644
--- a/src/test/java/net/objecthunter/exp4j/ExpressionTest.java
+++ b/src/test/java/net/objecthunter/exp4j/ExpressionTest.java
@@ -19,10 +19,7 @@
 
 import net.objecthunter.exp4j.function.Functions;
 import net.objecthunter.exp4j.operator.Operators;
-import net.objecthunter.exp4j.tokenizer.FunctionToken;
-import net.objecthunter.exp4j.tokenizer.NumberToken;
-import net.objecthunter.exp4j.tokenizer.OperatorToken;
-import net.objecthunter.exp4j.tokenizer.Token;
+import net.objecthunter.exp4j.tokenizer.*;
 
 import org.junit.Ignore;
 import org.junit.Test;
@@ -53,6 +50,18 @@ public void testExpression2() throws Exception{
         assertEquals(0d, exp.evaluate(), 0d);
     }
 
+    @Test
+    public void testGetVariableNames1() throws Exception{
+        Token[] tokens = new Token[] {
+                new VariableToken("a"),
+                new VariableToken("b"),
+                new OperatorToken(Operators.getBuiltinOperator('+', 2))
+        };
+        Expression exp = new Expression(tokens);
+
+        assertEquals(2, exp.getVariableNames().size());
+    }
+
     @Test
     @Ignore
     // If Expression should be threads safe this test must pass
diff --git a/src/test/java/net/objecthunter/exp4j/VariablesTest.java b/src/test/java/net/objecthunter/exp4j/VariablesTest.java
deleted file mode 100644
index 736d8a03..00000000
--- a/src/test/java/net/objecthunter/exp4j/VariablesTest.java
+++ /dev/null
@@ -1,42 +0,0 @@
-/* 
-* Copyright 2014 Frank Asseg
-*
-* Licensed under the Apache License, Version 2.0 (the "License");
-* you may not use this file except in compliance with the License.
-* You may obtain a copy of the License at
-*
-*    http://www.apache.org/licenses/LICENSE-2.0
-*
-* Unless required by applicable law or agreed to in writing, software
-* distributed under the License is distributed on an "AS IS" BASIS,
-* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-* See the License for the specific language governing permissions and
-* limitations under the License. 
-*/
-package net.objecthunter.exp4j;
-
-import net.objecthunter.exp4j.operator.Operators;
-import net.objecthunter.exp4j.tokenizer.OperatorToken;
-import net.objecthunter.exp4j.tokenizer.Token;
-import net.objecthunter.exp4j.tokenizer.VariableToken;
-
-import org.junit.Test;
-
-import static org.junit.Assert.assertEquals;
-
-
-public class VariablesTest {
-
-    @Test
-    public void testExpression1() throws Exception{
-        Token[] tokens = new Token[] {
-            new VariableToken("a"),
-            new VariableToken("b"),
-            new OperatorToken(Operators.getBuiltinOperator('+', 2))
-        };
-        Expression exp = new Expression(tokens);
-
-        assertEquals(2, exp.getVariableTokenNames().size());
-    }
-
-}