diff --git a/README.md b/README.md
index b1ea490..862fae4 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ Here is a sample ini file for the sample solution above:
 	Dependency ClrComponent.dll /u
 	Dependency ComCtl
 	
-`Identity` command is needed to produce `assemblyIdentity` tag in the output manifest. The  parameters of the command are `<exe_file>` and optional `[name]` and `[description]`. The path of the `<exe_file>` paramter sets the base path of the application, so that relative paths in next commands are based on this application path.
+`Identity` command is needed to produce `assemblyIdentity` tag in the output manifest. The  parameters of the command are `<exe_file>` and optional `[name]` and `[description]`. The path of the `<exe_file>` parameter sets the base path of the application, so that relative paths in next commands are based on this application path.
 
 ### Referencing COM components
 
diff --git a/Src/Ummm.vbp b/Src/Ummm.vbp
index 59f5e60..1259f57 100644
--- a/Src/Ummm.vbp
+++ b/Src/Ummm.vbp
@@ -10,17 +10,17 @@ Path32=".."
 Command32=""
 Name="Ummm"
 HelpContextID="0"
-Description="Unattended MMM 1.0.15"
+Description="Unattended MMM 1.0.16"
 CompatibleMode="0"
 MajorVer=1
 MinorVer=0
-RevisionVer=15
+RevisionVer=16
 AutoIncrementVer=0
 ServerSupportFiles=0
 VersionComments="Unattended MMM"
 VersionCompanyName="Unicontsoft"
-VersionFileDescription="Unattended MMM 1.0.15"
-VersionLegalCopyright="Copyright (c) 2009-2020 by wqweto@gmail.com"
+VersionFileDescription="Unattended MMM 1.0.16"
+VersionLegalCopyright="Copyright (c) 2009-2021 by wqweto@gmail.com"
 CompilationType=0
 OptimizationType=0
 FavorPentiumPro(tm)=0
diff --git a/Src/mdUmmm.bas b/Src/mdUmmm.bas
index 43ff77e..9b6fa10 100644
--- a/Src/mdUmmm.bas
+++ b/Src/mdUmmm.bas
@@ -2,7 +2,7 @@ Attribute VB_Name = "mdUmmm"
 '=========================================================================
 '
 '   Unattended Make My Manifest Project
-'   Copyright (c) 2009-2020 wqweto@gmail.com
+'   Copyright (c) 2009-2021 wqweto@gmail.com
 '
 '=========================================================================
 Option Explicit
@@ -614,8 +614,11 @@ Private Function pvDumpSupportedOs(vRow As Variant, cOutput As Collection) As Bo
         Case "win10"
             sGuid = "{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}"
         Case Else
-            '--- this has to be properly escaped attribute value
-            sGuid = At(vRow, lIdx)
+            If pvIsGuid(At(vRow, lIdx)) Then
+                sGuid = At(vRow, lIdx)
+            Else
+                sGuid = vbNullString
+            End If
         End Select
         If LenB(sGuid) <> 0 Then
             cOutput.Add Printf("            <supportedOS Id=""%1"" />", sGuid)
@@ -957,3 +960,9 @@ Private Function pvGetProgID(sClsID As String) As String
         Call CoTaskMemFree(lPtr)
     End If
 End Function
+
+Private Function pvIsGuid(ByVal sValue As String) As Boolean
+    Const EMPTY_GUID As String = "{00000000-0000-0000-0000-000000000000}"
+    pvIsGuid = sValue Like Replace(EMPTY_GUID, "0", "[0-9a-fA-F]")
+End Function
+