3 files changed, 30 insertions, 0 deletions

diff --git a/src/WixToolset.Core/ExtensibilityServices/PreprocessHelper.cs b/src/WixToolset.Core/ExtensibilityServices/PreprocessHelper.cs
index df301196..041c7d5d 100644
--- a/src/WixToolset.Core/ExtensibilityServices/PreprocessHelper.cs
+++ b/src/WixToolset.Core/ExtensibilityServices/PreprocessHelper.cs
@@ -386,6 +386,14 @@ namespace WixToolset.Core.ExtensibilityServices
                         }
                     }
 
+                    // Environment variables may contain parens so if it looks
+                    // like a function, check to see if the environment variable
+                    // prefix was explicitly provided.
+                    if (isFunction && remainder.StartsWith("(env.", StringComparison.Ordinal))
+                    {
+                        isFunction = false;
+                    }
+
                     // move the currentPosition to the closing paren
                     currentPosition += closingParenPosition;
 
diff --git a/src/test/WixToolsetTest.CoreIntegration/PreprocessorFixture.cs b/src/test/WixToolsetTest.CoreIntegration/PreprocessorFixture.cs
index a6504cb9..aad3ed73 100644
--- a/src/test/WixToolsetTest.CoreIntegration/PreprocessorFixture.cs
+++ b/src/test/WixToolsetTest.CoreIntegration/PreprocessorFixture.cs
@@ -40,6 +40,24 @@ namespace WixToolsetTest.CoreIntegration
         }
 
         [Fact]
+        /// <remarks>
+        /// This test will fail on 32-bit operating systems because it depends on "CommonProgramFiles(x86)"
+        /// which is only defined on 64-bit Windows.
+        /// </remarks>
+        public void SupportParensInEnvironmentVariables()
+        {
+            var folder = TestData.Get(@"TestData", "Preprocessor");
+
+            var serviceProvider = WixToolsetServiceProviderFactory.CreateServiceProvider();
+            var context = serviceProvider.GetService<IPreprocessContext>();
+            context.SourcePath = Path.Combine(folder, "EnvParens.wxs");
+
+            var preprocessor = serviceProvider.GetService<IPreprocessor>();
+            var result = preprocessor.Preprocess(context);
+            Assert.NotNull(result.Document);
+        }
+
+        [Fact]
         public void VariableRedefinitionIsAWarning()
         {
             var folder = TestData.Get(@"TestData\Variables");
diff --git a/src/test/WixToolsetTest.CoreIntegration/TestData/Preprocessor/EnvParens.wxs b/src/test/WixToolsetTest.CoreIntegration/TestData/Preprocessor/EnvParens.wxs
new file mode 100644
index 00000000..68d115c5
--- /dev/null
+++ b/src/test/WixToolsetTest.CoreIntegration/TestData/Preprocessor/EnvParens.wxs
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Wix xmlns="http://wixtoolset.org/schemas/v4/wxs">
+    <?define Test = "$(env.CommonProgramFiles(x86))" ?>
+</Wix>