diff --git a/SabreTools.Serialization/Deserializers/BSP.cs b/SabreTools.Serialization/Deserializers/BSP.cs
index aa7f1553..95df124b 100644
--- a/SabreTools.Serialization/Deserializers/BSP.cs
+++ b/SabreTools.Serialization/Deserializers/BSP.cs
@@ -28,7 +28,7 @@ namespace SabreTools.Serialization.Deserializers
 
             // Try to parse the header
             var header = data.ReadType<BspHeader>();
-            if (header?.Lumps == null)
+            if (header?.Lumps == null || header.Lumps.Length != BSP_HEADER_LUMPS)
                 return null;
             if (header.Version < 29 || header.Version > 30)
                 return null;
diff --git a/SabreTools.Serialization/Deserializers/VBSP.cs b/SabreTools.Serialization/Deserializers/VBSP.cs
index c8c89e69..abdf2596 100644
--- a/SabreTools.Serialization/Deserializers/VBSP.cs
+++ b/SabreTools.Serialization/Deserializers/VBSP.cs
@@ -32,7 +32,7 @@ namespace SabreTools.Serialization.Deserializers
                 return null;
             if (Array.IndexOf([17, 18, 19, 20, 21, 22, 23, 25, 27, 29, 0x00040014], header.Version) > -1)
                 return null;
-            if (header.Lumps == null)
+            if (header.Lumps == null || header.Lumps.Length != VBSP_HEADER_LUMPS)
                 return null;
 
             // Set the package header