diff --git a/core/src/main/java/com/schibsted/spt/data/jslt/parser/ParserImpl.java b/core/src/main/java/com/schibsted/spt/data/jslt/parser/ParserImpl.java
index f5acc006..bc4ab161 100644
--- a/core/src/main/java/com/schibsted/spt/data/jslt/parser/ParserImpl.java
+++ b/core/src/main/java/com/schibsted/spt/data/jslt/parser/ParserImpl.java
@@ -503,7 +503,13 @@ private static String makeString(ParseContext ctx, Token literal) {
         result[pos++] = ch;
       else {
         ch = string.charAt(++ix);
-
+        // special Regexp characters, s. https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html,
+        // "Predefined character classes".
+        if ("dDhHsSvVwW".contains(String.valueOf(ch))) {
+          result[pos++] = '\\';
+          result[pos++] = ch;
+          continue;
+        }
         switch (ch) {
         case '\\': result[pos++] = ch; break;
         case '"': result[pos++] = ch; break;
diff --git a/core/src/test/resources/function-tests.json b/core/src/test/resources/function-tests.json
index 49f28275..3408c03f 100644
--- a/core/src/test/resources/function-tests.json
+++ b/core/src/test/resources/function-tests.json
@@ -1128,15 +1128,20 @@
       "output": "\"\""
    },
    {
-      "query": "replace-regexp(., \"([0-9][0-9][0-9][0-9])-([0-9][0-9])-([0-9][0-9])\", \"$2/$3/$1\")",
+      "query": "replace-regexp(., \"(\\d{4})-(\\d{2})-(\\d{2})\", \"$2/$3/$1\")",
       "input" : "\"2019-12-31\"",
       "output": "\"12/31/2019\""
    },
    {
-      "query": "replace-regexp(., \"(?<year>[0-9][0-9][0-9][0-9])-(?<month>[0-9][0-9])-(?<day>[0-9][0-9])\", \"${day}.${month}.${year}\")",
+      "query": "replace-regexp(., \"(?<year>\\d{4})-(?<month>\\d{2})-(?<day>\\d{2})\", \"${day}.${month}.${year}\")",
       "input" : "\"2019-12-31\"",
       "output": "\"31.12.2019\""
    },
+   {
+      "query": "replace-regexp(., \"([a-z]+)\", \"$1\")",
+      "input" : "\"2019-12-31\"",
+      "output" : "\"2019-12-31\""
+   },
    {
       "query": "trim(.)",
       "input" : "\"some text\"",
diff --git a/core/src/test/resources/json-parse-error-tests.json b/core/src/test/resources/json-parse-error-tests.json
index 9a98f998..487245fb 100644
--- a/core/src/test/resources/json-parse-error-tests.json
+++ b/core/src/test/resources/json-parse-error-tests.json
@@ -1,7 +1,6 @@
 {
     "description" : "Tests that should cause the JSLT parser to declare JSON syntax error.",
     "tests" : [
-        "\" \\d \"",
         "\"\\u\"",
         "\"\\u0\"",
         "\"\\u00\"",
diff --git a/functions.md b/functions.md
index e41042a8..8fbc219b 100644
--- a/functions.md
+++ b/functions.md
@@ -523,10 +523,10 @@ If the `regexp` does not match the input,`out` corresponds to `value`.
 Examples:
 
 ```
-replace-regexp("2019-12-31", "([0-9][0-9][0-9][0-9])-([0-9][0-9])-([0-9][0-9])", "$2/$3/$1")
+replace-regexp("2019-12-31", "(\\d{4})-(\\d{2})-(\\d{2})", "$2/$3/$1")
    => "12/31/2019"
-replace-regexp("2019-12-31", "(?<year>[0-9][0-9][0-9][0-9])-(?<month>[0-9][0-9])-(?<day>[0-9][0-9])",
-   => "${day}.${month}.${year}") => "31.12.2019"
+replace-regexp("2019-12-31", "(?<year>\\d{4})-(?<month>\\d{2})-(?<day>\\d{2})", "${day}.${month}.${year}")
+   => "31.12.2019"
 replace-regexp("2019-12-31", "([a-z]+)", "$1")
    => "2019-12-31"
 ```