diff --git a/Library/DiscUtils.Vmdk/DiskImageFile.cs b/Library/DiscUtils.Vmdk/DiskImageFile.cs
index 1687f3613..e9cbdcbf4 100644
--- a/Library/DiscUtils.Vmdk/DiskImageFile.cs
+++ b/Library/DiscUtils.Vmdk/DiskImageFile.cs
@@ -145,6 +145,11 @@ internal DiskImageFile(FileLocator fileLocator, string file, FileAccess access)
             fileStream = fileLocator.Open(file, FileMode.Open, fileAccess, fileShare);
             LoadDescriptor(fileStream);
 
+            if (_descriptor is null)
+            {
+                throw new InvalidOperationException($"This VMDK image file does not contain an embedded descriptor");
+            }
+
             // For monolithic disks, keep hold of the stream - we won't try to use the file name
             // from the embedded descriptor because the file may have been renamed, making the 
             // descriptor out of date.