diff --git a/common.scad b/common.scad
index 9ffade5..c172cbb 100644
--- a/common.scad
+++ b/common.scad
@@ -577,6 +577,7 @@ module no_module() {
 
 
 function _valstr(x) =
+    is_string(x)? str("\"",str_replace_char(x, "\"", "\\\""),"\"") :
     is_list(x)? str("[",str_join([for (xx=x) _valstr(xx)],","),"]") :
     is_num(x) && x==floor(x)? fmt_int(x) :
     is_finite(x)? fmt_float(x,12) : x;
diff --git a/strings.scad b/strings.scad
index 1577aee..732595f 100644
--- a/strings.scad
+++ b/strings.scad
@@ -734,7 +734,7 @@ function str_pad(str,length,char=" ",left=false) =
 //   can be any string.  
 function str_replace_char(str,char,replace) =
    assert(is_str(str))
-   assert(is_str(char) && len(char)==1, "Search pattern 'char' must be a a single character string")
+   assert(is_str(char) && len(char)==1, "Search pattern 'char' must be a single character string")
    assert(is_str(replace))
    str_join([for(c=str) c==char ? replace : c]);