1 files changed, 1 insertions, 1 deletions

diff --git a/src/WixToolset.Core/CommandLine/BuildCommand.cs b/src/WixToolset.Core/CommandLine/BuildCommand.cs
index 5ee60984..023a3c1e 100644
--- a/src/WixToolset.Core/CommandLine/BuildCommand.cs
+++ b/src/WixToolset.Core/CommandLine/BuildCommand.cs
@@ -591,7 +591,7 @@ namespace WixToolset.Core.CommandLine
                     this.OutputType = Path.GetExtension(this.OutputFile);
                 }
 
-                switch (this.OutputType.ToLowerInvariant())
+                switch (this.OutputType?.ToLowerInvariant())
                 {
                     case "bundle":
                     case ".exe":