Index: includes/forminputs/SF_TextWithAutocompleteInput.php
===================================================================
--- includes/forminputs/SF_TextWithAutocompleteInput.php	(revision 104239)
+++ includes/forminputs/SF_TextWithAutocompleteInput.php	(working copy)
@@ -176,6 +176,9 @@
 		if ( array_key_exists( 'placeholder', $other_args ) ) {
 			$inputAttrs['placeholder'] = $other_args['placeholder'];
 		}
+		if ( array_key_exists( 'existing values only', $other_args ) ) {
+			$inputAttrs['existingvaluesonly'] = 'true';
+		}
 		$text = "\n\t" . Xml::element( 'input', $inputAttrs ) . "\n";
 
 		if ( array_key_exists( 'uploadable', $other_args ) && $other_args['uploadable'] == true ) {
@@ -224,6 +227,12 @@
 	public static function getParameters() {
 		$params = parent::getParameters();
 		$params = array_merge( $params, self::getAutocompletionParameters() );
+		$params[] = array(
+			'name' => 'existing values only',
+			'type' => 'boolean',
+			'description' => wfMsg( 'sf_forminputs_existingvaluesonly' )
+		);
+
 		return $params;
 	}
 
Index: libs/SemanticForms.js
===================================================================
--- libs/SemanticForms.js	(revision 104239)
+++ libs/SemanticForms.js	(working copy)
@@ -475,6 +475,14 @@
 	if (isEmpty) {
 		this.addErrorMessage(sfgBlankErrorStr);
 		return false;
+	} else if (this.find("input").attr("existingvaluesonly") == 'true'){
+		var settings = this.find("input").attr("autocompletesettings");
+		var isValueExist = (jQuery.inArray(this.find("input").val(), sfgAutocompleteValues[settings]) != -1);
+		if (!isValueExist) {
+			this.addErrorMessage(sfgBlankErrorStr);
+			return false;
+		}
+		return true;
 	} else {
 		return true;
 	}
@@ -484,6 +492,13 @@
 	if (this.find("input").val() == '') {
 		this.addErrorMessage(sfgBlankErrorStr);
 		return false;
+	} else if (this.find("select").attr("existingvaluesonly") == 'true') {
+		var isValueExist = (this.find("select").find("[value='" + this.find("input").val() + "']").size() != 0);
+		if (!isValueExist) {
+			this.addErrorMessage(sfgBlankErrorStr);
+			return false;
+		}
+		return true;
 	} else {
 		return true;
 	}
@@ -901,13 +916,7 @@
 					},
 					delay: 0,
 					change: function(event, ui) {
-						if (!ui.item) {
-							if (select.attr("existingvaluesonly") == 'true') {
-								// remove invalid value, as it didn't match anything
-								jQuery(this).val("");
-							}
-							return false;
-						}
+						if (!ui.item) return false;
 						select.val(ui.item.id);
 						self._trigger("selected", event, {
 							item: select.find("[value='" + ui.item.id + "']")