diff --git a/NetworkPkg/IScsiDxe/IScsiMisc.c b/NetworkPkg/IScsiDxe/IScsiMisc.c
index 05f639aaee..aeb99e5f94 100644
--- a/NetworkPkg/IScsiDxe/IScsiMisc.c
+++ b/NetworkPkg/IScsiDxe/IScsiMisc.c
@@ -226,6 +226,7 @@ IScsiLunToUnicodeStr (
   //
   // Remove the last '-'
   //
+  ASSERT (StrLen(Str) >= 1);
   Str[StrLen (Str) - 1] = 0;
 
   for (Index = StrLen (Str) - 1; Index > 1; Index = Index - 2) {