diff --git a/luaxp.lua b/luaxp.lua
index d1663d7..43a4314 100644
--- a/luaxp.lua
+++ b/luaxp.lua
@@ -57,7 +57,8 @@ local TNUL = 'null'
 local NULLATOM = { __type=TNUL }
 setmetatable( NULLATOM, { __tostring=function() return "null" end } )
 
-local charmap = { t = "\t", r = "\r", n = "\n" }
+local charmap = { t = "\t", r = "\r", n = "\n",
+                  ["\\"] = "\\", ["'"] = "'", ['"'] = '"' }
 
 local reservedWords = {
       ['false']=false, ['true']=true
@@ -440,6 +441,14 @@ local function xp_mktime( yy, mm, dd, hours, mins, secs )
     return os.time(pt)
 end
 
+local function xp_enquote(s, q)
+    if base.type(s) ~= "string" then evalerror("String required") end
+    if q ~= "'" and q ~= '"' then evalerror("Illegal quotation mark") end
+    s = s:gsub("\\", "\\\\")
+    s = s:gsub(q, "\\" .. q)
+    return q .. s .. q
+end
+
 local function xp_rtrim(s)
     if base.type(s) ~= "string" then evalerror("String required") end
     return s:gsub("%s+$", "")
@@ -747,7 +756,7 @@ local function scan_fref( expr, index, name )
             -- Start of string?
             local qq = ch
             index, ch = scan_string( expr, index )
-            subexp = subexp .. qq .. ch.value .. qq
+            subexp = subexp .. xp_enquote(ch.value, qq)
         elseif ch == ',' and parenLevel == 1 then -- completed subexpression
             subexp = xp_trim( subexp )
             D("scan_fref: handling argument=%1", subexp)
diff --git a/test/test.lua b/test/test.lua
index c65d3c2..e3b6e43 100644
--- a/test/test.lua
+++ b/test/test.lua
@@ -374,6 +374,9 @@ local function doStringFuncTests()
     eval("sub('The rain in Spain stays mainly in the plain.', 35, -5)", "the pl")
     eval("sub('The rain in Spain stays mainly in the plain.', 39)", "plain.")
     eval("sub('[in brackets]', 2, -2)", "in brackets")
+    eval("sub('Jack\\'s house', 1, 6)", "Jack's")
+    eval("sub('A back slash (\\\\) is a screening character', 14, 16)", "(\\)")
+    eval('sub("Start from a \\"Hello, World!\\" program", 14, 28)', '"Hello, world!"')
     eval("find('The rain in Spain stays mainly in the plain.', 'not there')", 0)
     eval("find('The rain in Spain stays mainly in the plain.', 'plain.')", 39)
     eval("upper('The rain in Spain stays mainly in the plain.')", "THE RAIN IN SPAIN STAYS MAINLY IN THE PLAIN.")