diff --git a/CHANGELOG.md b/CHANGELOG.md
index 723c870d..b80ee968 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,10 +1,11 @@
 # Clixon Changelog
 
-## 3.10.0/4.0.0 (Upcoming)
+## 4.0.0 (Upcoming)
 
 ### Major New features
 * Regexp improvements: Libxml2 XSD, multiple patterns, optimization
   * Support for multiple patterns as described in RFC7950 Section 9.4.7
+  * Support for inverted patterns as described in RFC7950 Section 9.4.6
   * Libxml2 support for full XSD matching as alternative to Posix translation
     * Configure with: `./configure --with-libxml2`	
     * Set `CLICON_YANG_REGEXP` to libxml2 (default is posix)
diff --git a/README.md b/README.md
index c97cb4ef..c5509c03 100644
--- a/README.md
+++ b/README.md
@@ -115,11 +115,27 @@ However, the following YANG syntax modules are not implemented (reference to RFC
 - refine (7.13.2)
 - status (7.21.2)
 - extension (7.19)
-- modifier (9.4.6)
 - YIN (13)
 - Yang extended Xpath functions: re-match(), deref)(), derived-from(), derived-from-or-self(), enum-value(), bit-is-set() (10.2-10.6)
 - Default values on leaf-lists are not supported (7.7.2)
 
+### Yang patterns
+Yang type patterns use regexps defined in [W3C XML XSD](http://www.w3.org/TR/2004/REC-xmlschema-2-20041028). XSD regexp:s are
+slightly different from POSIX regexp.
+
+Clixon supports two regular expressions engines:
+  * "Posix" which is the default method, which _translates_ XSD regexp:s to posix before matching with the standard Linux regex engine. This translation is not complete but can be considered "good-enough" for most yang use-cases. For reference, all standard Yang models in [https://github.com/YangModels/yang] have been tested.
+  * "Libxml2" which uses the XSD regex engine in Libxml2. This is a complete XSD engine but you need to compile and link with libxml2 which may add overhead.
+
+To use libxml2 in clixon you need enable libxml2 in both cligen and clixon:
+```
+> ./configure --with-libxml2 # both cligen and clixon
+```
+You then need to set the following configure option:
+```
+  <CLICON_YANG_REGEXP>libxml2</CLICON_YANG_REGEXP>
+```
+
 ## XML
 
 Clixon has its own implementation of XML and XPATH implementation.
diff --git a/apps/cli/cli_generate.c b/apps/cli/cli_generate.c
index a78d55f1..69b360ae 100644
--- a/apps/cli/cli_generate.c
+++ b/apps/cli/cli_generate.c
@@ -287,21 +287,30 @@ yang2cli_var_pattern(clicon_handle h,
     char   *mode;
     cg_var *cvp;
     char   *pattern;
+    int     invert;
+    char   *posix;
     
     mode = clicon_yang_regexp(h);
     cvp = NULL; /* Loop over compiled regexps */
     while ((cvp = cvec_each(patterns, cvp)) != NULL){
 	pattern = cv_string_get(cvp);
+	invert = cv_flag(cvp, V_INVERT);
 	if (strcmp(mode, "posix") == 0){
-	    char   *posix = NULL;
+	    posix = NULL;
 	    if (regexp_xsd2posix(pattern, &posix) < 0)
 		goto done;
-	    cprintf(cb, " regexp:\"%s\"", posix);
-	    if (posix)
+	    cprintf(cb, " regexp:%s\"%s\"",
+		    invert?"!":"",
+		    posix);
+	    if (posix){
 		free(posix);
+		posix = NULL;
+	    }
 	}
 	else
-	    cprintf(cb, " regexp:\"%s\"", pattern);
+	    cprintf(cb, " regexp:%s\"%s\"",
+		    invert?"!":"",
+		    pattern);
     }
     retval = 0;
  done:
diff --git a/doc/FAQ.md b/doc/FAQ.md
index fc71e607..c052e9ae 100644
--- a/doc/FAQ.md
+++ b/doc/FAQ.md
@@ -27,7 +27,6 @@
   * [How should I start the backend daemon?](#how-should-i-start-the-backend-daemon)
   * [Can I use systemd with Clixon?](#can-i-use-systemd-with-clixon)
   * [How can I add extra XML?](#how-can-i-add-extra-xml)
-  * [What about Regexps?](#what-about-regexps)
   * [I want to program. How do I extend the example?](#i-want-to-program-how-do-i-extend-the-example)
   * [How is a plugin initiated?](#how-is-a-plugin-initiated)
   * [How do I write a commit function?](#how-do-i-write-a-commit-function)
@@ -439,26 +438,6 @@ You add this via the -c option:
 The second way is by programming the plugin_reset() in the backend
 plugin. The example code contains an example on how to do this (see plugin_reset() in example_backend.c).
 
-## What about Regexps?
-
-Yang type patterns use regexps defined in [W3C XML XSD
-](http://www.w3.org/TR/2004/REC-xmlschema-2-20041028). XSD regexp:s are
-slightly different from POSIX regexp.
-
-lixon supports two regular expressions engines:
-* "Posix" which is the default method, _translates_ XSD regexp:s to posix before matching with the standard Linux regex engine. This translation is not complete but considered
-"good-enough" for most yang use-cases. For reference, all standard
-Yang models in [https://github.com/YangModels/yang] have been tested.
-* "Libxml2" which uses the XSD regex engine in Libxml2. This is a complete XSD engine but you need to compile and link with libxml2 which may add overhead.
-
-To use libxml2 in clixon you need enable libxml2 in both cligen and clixon:
-```
-> ./configure --with-libxml2 # both cligen and clixon
-```
-You then need to set the following configure option:
-```
-  <CLICON_YANG_REGEXP>libxml2</CLICON_YANG_REGEXP>
-```
 
 ## I want to program. How do I extend the example?
 See [../example/main](../example/main)
diff --git a/lib/src/clixon_yang.c b/lib/src/clixon_yang.c
index 144990da..cd47c102 100644
--- a/lib/src/clixon_yang.c
+++ b/lib/src/clixon_yang.c
@@ -1368,8 +1368,6 @@ ys_populate_leaf(clicon_handle h,
     if (yparent && yparent->ys_keyword == Y_LIST){
 	if ((ret = yang_key_match(yparent, ys->ys_argument)) < 0)
 	    goto done;
-	if (ret == 1)
-	    cv_flag_set(cv, V_UNIQUE);
     }
     ys->ys_cv = cv;
     retval = 0;
diff --git a/lib/src/clixon_yang_internal.h b/lib/src/clixon_yang_internal.h
index f36692ff..acf7d416 100644
--- a/lib/src/clixon_yang_internal.h
+++ b/lib/src/clixon_yang_internal.h
@@ -41,10 +41,12 @@
 
 
 /*
- * Actually cligen variable stuff XXX
+ * Clixon-specific cligen variable (cv) flags
+ * CLIgen flags defined are in the range 0x01 -0x0f
+ * An application can use any flags above that
+ * @see cv_flag
  */
-#define V_UNIQUE	0x01	/* Variable flag */
-#define V_UNSET		0x08	/* Variable is unset, ie no default */
+#define V_UNSET	  0x10	/* Used by XML code to denote a value is not default */
 
 
 #define YANG_FLAG_MARK 0x01  /* Marker for dynamic algorithms, eg expand */
diff --git a/lib/src/clixon_yang_type.c b/lib/src/clixon_yang_type.c
index 34b1cf2a..702093d0 100644
--- a/lib/src/clixon_yang_type.c
+++ b/lib/src/clixon_yang_type.c
@@ -33,8 +33,9 @@
 
  * Yang type related functions
  * Part of this is type resolving which is pretty complex
- * 
- * (called at parse / set cache)
+ *                   +--> yang_type_cache_set
+ *                   +--> compile_pattern2regexp
+ * (called at parse) |
  * ys_resolve_type  --+     ys_populate_range, yang_enum_int_value(NULL)
  *                     \    |  cml
  *                      v   v  v
@@ -43,9 +44,10 @@
  * ^  ^                     ^  ^
  * |  |                     |  |
  * |  yang2cli_var          |  yang2cli_var_union_one
- * ys_cv_validate           ys_cv_validate_union_one
- * |
- * ys_populate_leaf, xml_cv_cache (NULL)
+ * ys_cv_validate----+      ys_cv_validate_union_one
+ * |                  \    /
+ * ys_populate_leaf,   +--> cv_validate1 --> cv_validate_pattern (exec regexps)
+ * xml_cv_cache (NULL)
  */
 
 #ifdef HAVE_CONFIG_H
@@ -278,13 +280,15 @@ yang_type_cache_free(yang_type_cache *ycache)
     return 0;
 }
 
-/* Compile yang patterns in string form to regex compiled void* form
+/*! Compile yang patterns in string form to regex compiled void* form
  * and re-store into "patterns" cvec.
  * This is done here instead of deep in resolve code (resolve_restrictions)
  * since it id dependent on clicon_handle.
  * The downside is that all accesses to "patterns" must pass via the cache.
  * If calls to yang_type_resolve is made without the cache is set, will be
  * wrong.
+ * @see match_regexp  in cligen code
+ * @see yang_type_resolve_restrictions  where patterns is set
  */
 static int
 compile_pattern2regexp(clicon_handle h,
@@ -317,6 +321,9 @@ compile_pattern2regexp(clicon_handle h,
 	    goto done;
 	}
 	cv_void_set(rcv, re);
+	/* invert pattern check */
+	if (cv_flag(pcv, V_INVERT))
+	    cv_flag_set(rcv, V_INVERT);
     }
     retval = 1;
  done:
@@ -515,6 +522,8 @@ cv_validate_pattern(clicon_handle h,
 	re = cv_void_get(cvr);
 	if ((ret = regex_exec(h, re, str?str:"")) < 0)
 	    goto done;
+	if (cv_flag(cvr, V_INVERT))
+	    ret = !ret; /* swap 0 and 1 */
 	if (ret == 0){
 	    if (reason)
 		*reason = cligen_reason("regexp match fail: pattern does not match %s",
@@ -1062,11 +1071,11 @@ yang_find_identity(yang_stmt *ys,
  * @retval     0         OK. 
  */
 static int
-resolve_restrictions(yang_stmt   *ytype,
-		     int         *options, 
-		     cvec       **cvv, 
-		     cvec        *regexps,
-		     uint8_t     *fraction)
+yang_type_resolve_restrictions(yang_stmt   *ytype,
+			       int         *options, 
+			       cvec       **cvv, 
+			       cvec        *regexps,
+			       uint8_t     *fraction)
 {
     int        retval = -1;
     yang_stmt *ys;
@@ -1094,6 +1103,9 @@ resolve_restrictions(yang_stmt   *ytype,
 		goto done;
 	    }
 	    pattern = ys->ys_argument; /* clear text pattern */
+	    /* Check 1.1 invert pattern */
+	    if (yang_find(ys, Y_MODIFIER, "invert-match") != NULL)
+		cv_flag_set(cv, V_INVERT);
 	    cv_string_set(cv, pattern);
 	}
     }
@@ -1165,7 +1177,7 @@ yang_type_resolve(yang_stmt   *yorig,
     /* Check if type is basic type. If so, return that */
     if ((prefix == NULL && yang_builtin(type))){
 	*yrestype = ytype; 
-	if (resolve_restrictions(ytype, options, cvv, patterns, fraction) < 0)
+	if (yang_type_resolve_restrictions(ytype, options, cvv, patterns, fraction) < 0)
 	    goto done;
 	goto ok;
     }
@@ -1210,7 +1222,7 @@ yang_type_resolve(yang_stmt   *yorig,
 			      fraction) < 0)
 	    goto done;
 	/* appends patterns, overwrites others if any */
-	if (resolve_restrictions(ytype, options, cvv, patterns, fraction) < 0)
+	if (yang_type_resolve_restrictions(ytype, options, cvv, patterns, fraction) < 0)
 	    goto done;
     }
   ok:
diff --git a/test/test_pattern.sh b/test/test_pattern.sh
index d546c667..36322a35 100755
--- a/test/test_pattern.sh
+++ b/test/test_pattern.sh
@@ -64,11 +64,9 @@ module pattern{
          type string {
             length "1..max";
             pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*';
-/*
             pattern '[xX][mM][lL].*' {
                modifier invert-match;
             }
-*/
          }
       }
       typedef twomatchtype {
@@ -409,7 +407,7 @@ testrun rfc2 0 'xx00'
 new "Test for RFC7950 Sec 9.4.7 pattern example 3 (invert match)"
 testrun rfc3 1 'enabled'
 testrun rfc3 0 '10-mbit'
-#testrun rfc3 0 'xml-element' # invert-match dont work
+testrun rfc3 0 'xml-element' # invert: dont match xml
 
 new "Test for two patterns"
 testrun 'twomatch' 1 'gksdhfsakjhdksa'
@@ -717,6 +715,9 @@ expectfn "$clixon_cli -1f $cfg -l o set c rfc3 enabled" 0 '^$'
 new "CLI tests for RFC7950 Sec 9.4.7 ex 3 10-mbit (should fail)"
 expectfn "$clixon_cli -1f $cfg -l o set c rfc3 10-mbit" 255 '^CLI syntax error:'
 
+new "CLI tests for RFC7950 Sec 9.4.7 ex 3 xml-element (should fail)"
+expectfn "$clixon_cli -1f $cfg -l o set c rfc3 xml-element" 255 '^CLI syntax error:'
+
 new "CLI tests for two patterns gksdhfsakjhdks"
 expectfn "$clixon_cli -1f $cfg -l o set c twomatch gksdhfsakjhdks" 0 '^$'
 
diff --git a/util/clixon_util_regexp.c b/util/clixon_util_regexp.c
index 1687a32d..d0990ef7 100644
--- a/util/clixon_util_regexp.c
+++ b/util/clixon_util_regexp.c
@@ -96,8 +96,8 @@ regex_posix(char *regexp,
 	    int   nr,
 	    int   debug)
 {
-    int        retval = -1;
-    char       *posix = NULL;
+    int     retval = -1;
+    char   *posix = NULL;
     char    pattern[1024];
     int     status = 0;
     regex_t re;