diff --git a/nselib/mssql.lua b/nselib/mssql.lua
index 2f4aaf19b..7124dae14 100644
--- a/nselib/mssql.lua
+++ b/nselib/mssql.lua
@@ -1718,13 +1718,8 @@ PreLoginPacket =
       end
 
       if ( optionType == PreLoginPacket.OPTION_TYPE.Version ) then
-        local major, minor, build, subBuild, version
-        major = string.byte( optionData:sub( 1, 1 ) )
-        minor = string.byte( optionData:sub( 2, 2 ) )
-        build = (string.byte( optionData:sub( 3, 3 ) ) * 256) + string.byte( optionData:sub( 4, 4 ) )
-        subBuild = (string.byte( optionData:sub( 5, 5 ) ) * 256) + string.byte( optionData:sub( 6, 6 ) )
-
-        version = SqlServerVersionInfo:new()
+        local major, minor, build, subBuild = (">BBI2I2"):unpack(optionData)
+        local version = SqlServerVersionInfo:new()
         version:SetVersion( major, minor, build, subBuild, "SSNetLib" )
         preLoginPacket.versionInfo = version
       elseif ( optionType == PreLoginPacket.OPTION_TYPE.Encryption ) then
diff --git a/nselib/smb.lua b/nselib/smb.lua
index 2574abfd3..be9f68241 100644
--- a/nselib/smb.lua
+++ b/nselib/smb.lua
@@ -3482,7 +3482,7 @@ function get_uniqueish_name(host, extension, seed)
   local str = lhost .. (seed or "") .. (extension or "") .. (nmap.registry.args.randomseed or "")
 
   for i = 1, #str, 1 do
-    local chr = string.byte(string.sub(str, i, i), 1)
+    local chr = str:byte(i)
     hash = bit.bxor(hash, chr)
     hash = bit.bor(bit.lshift(hash, 3), bit.rshift(hash, 29))
     hash = bit.bxor(hash, 3)
diff --git a/scripts/vtam-enum.nse b/scripts/vtam-enum.nse
index 3dea2cb0b..3f465ecb9 100644
--- a/scripts/vtam-enum.nse
+++ b/scripts/vtam-enum.nse
@@ -87,7 +87,7 @@ local function screen_diff( orig_screen, current_screen )
   if #orig_screen == 0 or #current_screen == 0 then return 0 end
   local m = 1
   for i =1 , #orig_screen do
-    if orig_screen:sub(i,i) == current_screen:sub(i,i) then
+    if orig_screen:byte(i) == current_screen:byte(i) then
       m = m + 1
     end
   end