diff --git a/Shared.Tests/Transformations/Common/ExpressionTest.cs b/Shared.Tests/Transformations/Common/ExpressionTest.cs
index 13940203..fa1b5c0b 100644
--- a/Shared.Tests/Transformations/Common/ExpressionTest.cs
+++ b/Shared.Tests/Transformations/Common/ExpressionTest.cs
@@ -309,5 +309,38 @@ public void TestShouldSupportPowOperator()
 
             Assert.AreEqual("$small_150,$big_$small_pow_1.5", transformation.Generate());
         }
+
+        [TestCase(null, null)]
+        [TestCase("", null)]
+        [TestCase(" ", "_")]
+        [TestCase("   ", "_")]
+        [TestCase("_", "_")]
+        [TestCase("___", "_")]
+        [TestCase(" _ __  _", "_")]
+        [TestCase("foobar", "foobar")]
+        [TestCase("foo && bar", "foo_and_bar")]
+        [TestCase("foo&&bar", "foo&&bar")]
+        [TestCase("width", "w")]
+        [TestCase("initial_aspect_ratio", "iar")]
+        [TestCase("$width", "$width")]
+        [TestCase("$initial_aspect_ratio", "$initial_ar")]
+        [TestCase("$mywidth", "$mywidth")]
+        [TestCase("$widthwidth", "$widthwidth")]
+        [TestCase("$_width", "$_width")]
+        [TestCase("$__width", "$_width")]
+        [TestCase("$$width", "$$width")]
+        [TestCase("$height_100", "$height_100")]
+        [TestCase("$heightt_100", "$heightt_100")]
+        [TestCase("$$height_100", "$$height_100")]
+        [TestCase("$heightmy_100", "$heightmy_100")]
+        [TestCase("$myheight_100", "$myheight_100")]
+        [TestCase("$heightheight_100", "$heightheight_100")]
+        [TestCase("$theheight_100", "$theheight_100")]
+        [TestCase("$__height_100", "$_height_100")]
+        public void TestNormalizeExpressionComplexCases(string expression, string expected)
+        {
+            var actual = Expression.Normalize(expression);
+            Assert.AreEqual(expected, actual);
+        }
     }
 }
diff --git a/Shared.Tests/Transformations/Common/TransformationTest.cs b/Shared.Tests/Transformations/Common/TransformationTest.cs
index cca03561..f5dcf0d4 100644
--- a/Shared.Tests/Transformations/Common/TransformationTest.cs
+++ b/Shared.Tests/Transformations/Common/TransformationTest.cs
@@ -171,5 +171,19 @@ public void TestVideoLayersUnmodifiableFields()
             Assert.Throws<InvalidOperationException>(() => textLayer.Format(testValue));
             Assert.Throws<InvalidOperationException>(() => textLayer.Type(testValue));
         }
+
+        [Test]
+        public void TestUserVariableNamesContainingPredefinedNamesAreNotAffected()
+        {
+            var transformation = new Transformation()
+                .Variable("$mywidth", "100")
+                .Variable("$aheight", 300)
+                .Chain()
+                .Width("3 + $mywidth * 3 + 4 / 2 * initialWidth * $mywidth")
+                .Height("3 * initialHeight + $aheight");
+
+            const string expected = "$aheight_300,$mywidth_100/h_3_mul_ih_add_$aheight,w_3_add_$mywidth_mul_3_add_4_div_2_mul_iw_mul_$mywidth";
+            Assert.AreEqual(expected, transformation.Generate());
+        }
     }
 }
diff --git a/Shared/Transforms/BaseExpression.cs b/Shared/Transforms/BaseExpression.cs
index ebfd2555..ce9f2487 100644
--- a/Shared/Transforms/BaseExpression.cs
+++ b/Shared/Transforms/BaseExpression.cs
@@ -104,8 +104,25 @@ public static string Normalize(string expression)
             }
 
             expression = Regex.Replace(expression, "[ _]+", "_");
-            string pattern = GetPattern();
-            return Regex.Replace(expression, pattern, m => GetOperatorReplacement(m.Value));
+            const string userVariablePattern = "\\$_*[^_]+";
+
+            var generalPattern = GetPattern();
+            var matcher = new Regex(userVariablePattern, RegexOptions.IgnoreCase).Match(expression);
+            var sb = new StringBuilder();
+            var lastMatchEnd = 0;
+            while (matcher.Success)
+            {
+                var matcherGroup = matcher.Groups[0];
+                var beforeMatch = expression.Substring(lastMatchEnd, matcherGroup.Index - lastMatchEnd);
+                sb.Append(Regex.Replace(beforeMatch, generalPattern, m => GetOperatorReplacement(m.Value)));
+                sb.Append(matcherGroup.Value);
+                lastMatchEnd = matcherGroup.Index + matcherGroup.Length;
+                matcher = matcher.NextMatch();
+            }
+
+            var tail = expression.Substring(lastMatchEnd);
+            sb.Append(Regex.Replace(tail, generalPattern, m => GetOperatorReplacement(m.Value)));
+            return sb.ToString();
         }
 
         /// <summary>