diff --git a/resources/rendertheme.xsd b/resources/rendertheme.xsd
index cdfc815c..a2c03204 100644
--- a/resources/rendertheme.xsd
+++ b/resources/rendertheme.xsd
@@ -303,10 +303,10 @@
 
     <!-- tag-transform element -->
     <xs:complexType name="tag-transform">
-        <xs:attribute name="k" type="xs:string" use="required" />
-        <xs:attribute name="v" type="xs:string" use="optional" />
-        <xs:attribute name="k-match" type="xs:string" use="required" />
-        <xs:attribute name="v-match" type="xs:string" use="optional" />
+        <xs:attribute name="match-k" type="xs:string" use="required" />
+        <xs:attribute name="match-v" type="xs:string" use="optional" />
+        <xs:attribute name="output-k" type="xs:string" use="required" />
+        <xs:attribute name="output-v" type="xs:string" use="optional" />
     </xs:complexType>
 
     <!-- rendertheme element -->
diff --git a/vtm-themes/resources/assets/vtm/mapzen.xml b/vtm-themes/resources/assets/vtm/mapzen.xml
index ec17fc38..79b138bd 100644
--- a/vtm-themes/resources/assets/vtm/mapzen.xml
+++ b/vtm-themes/resources/assets/vtm/mapzen.xml
@@ -3,16 +3,16 @@
     version="1" xmlns="http://opensciencemap.org/rendertheme"
     xsi:schemaLocation="http://opensciencemap.org/rendertheme https://raw.githubusercontent.com/mapsforge/vtm/master/resources/rendertheme.xsd">
 
-    <!--<tag-transform k="kind" v="building" k-match="building" v-match="yes" />-->
-    <!--<tag-transform k="kind" v="building_part" k-match="building:part" v-match="yes" />-->
-    <tag-transform k="root_id" k-match="ref" />
+    <!--<tag-transform match-k="building" match-v="yes" output-k="kind" output-v="building" />-->
+    <!--<tag-transform match-k="building:part" match-v="yes" output-k="kind" output-v="building_part" />-->
+    <tag-transform match-k="ref" output-k="root_id" />
 
-    <tag-transform k="roof_color" k-match="roof:colour" />
-    <tag-transform k="roof_direction" k-match="roof:direction" />
-    <tag-transform k="roof_height" k-match="roof:height" />
-    <tag-transform k="roof_material" k-match="roof:material" />
-    <tag-transform k="roof_orientation" k-match="roof:orientation" />
-    <tag-transform k="roof_shape" k-match="roof:shape" />
+    <tag-transform match-k="roof:colour" output-k="roof_color" />
+    <tag-transform match-k="roof:direction" output-k="roof_direction" />
+    <tag-transform match-k="roof:height" output-k="roof_height" />
+    <tag-transform match-k="roof:material" output-k="roof_material" />
+    <tag-transform match-k="roof:orientation" output-k="roof_orientation" />
+    <tag-transform match-k="roof:shape" output-k="roof_shape" />
 
     <!-- base style for fixed width lines -->
     <style-line cap="butt" fix="true" id="fix" width="1.0" />
diff --git a/vtm-themes/resources/assets/vtm/openmaptiles.xml b/vtm-themes/resources/assets/vtm/openmaptiles.xml
index 01f8ad34..7563d0d4 100644
--- a/vtm-themes/resources/assets/vtm/openmaptiles.xml
+++ b/vtm-themes/resources/assets/vtm/openmaptiles.xml
@@ -3,10 +3,10 @@
     version="1" xmlns="http://opensciencemap.org/rendertheme"
     xsi:schemaLocation="http://opensciencemap.org/rendertheme https://raw.githubusercontent.com/mapsforge/vtm/master/resources/rendertheme.xsd">
 
-    <tag-transform k="render_height" k-match="height" />
-    <tag-transform k="render_min_height" k-match="min_height" />
-    <!--<tag-transform k="layer" v="building" k-match="building" v-match="yes" />-->
-    <!--<tag-transform k="layer" v="building:part" k-match="building:part" v-match="yes" />-->
+    <tag-transform match-k="height" output-k="render_height" />
+    <tag-transform match-k="min_height" output-k="render_min_height" />
+    <!--<tag-transform match-k="building" match-v="yes" output-k="layer" output-v="building" />-->
+    <!--<tag-transform match-k="building:part" match-v="yes" output-k="layer" output-v="building:part" />-->
 
     <!--###### TEXT styles ######-->
 
diff --git a/vtm/src/org/oscim/theme/XmlThemeBuilder.java b/vtm/src/org/oscim/theme/XmlThemeBuilder.java
index d9d9a5a9..08f2db95 100644
--- a/vtm/src/org/oscim/theme/XmlThemeBuilder.java
+++ b/vtm/src/org/oscim/theme/XmlThemeBuilder.java
@@ -1,7 +1,7 @@
 /*
  * Copyright 2010, 2011, 2012 mapsforge.org
  * Copyright 2013 Hannes Janetzek
- * Copyright 2016-2018 devemux86
+ * Copyright 2016-2019 devemux86
  * Copyright 2016-2017 Longri
  * Copyright 2016 Andrey Novikov
  * Copyright 2018 Gustl22
@@ -1268,40 +1268,40 @@ public class XmlThemeBuilder extends DefaultHandler {
     }
 
     private void tagTransform(String localName, Attributes attributes) {
-        String k, v, matchKey, matchValue;
-        k = v = matchKey = matchValue = null;
+        String matchKey, matchValue, outputKey, outputValue;
+        matchKey = matchValue = outputKey = outputValue = null;
 
         for (int i = 0; i < attributes.getLength(); i++) {
             String name = attributes.getLocalName(i);
             String value = attributes.getValue(i);
 
             switch (name) {
-                case "k":
-                    k = value;
-                    break;
-                case "v":
-                    v = value;
-                    break;
-                case "k-match":
+                case "match-k":
                     matchKey = value;
                     break;
-                case "v-match":
+                case "match-v":
                     matchValue = value;
                     break;
+                case "output-k":
+                    outputKey = value;
+                    break;
+                case "output-v":
+                    outputValue = value;
+                    break;
                 default:
                     logUnknownAttribute(localName, name, value, i);
             }
         }
 
-        if (k == null || k.isEmpty() || matchKey == null || matchKey.isEmpty()) {
+        if (matchKey == null || matchKey.isEmpty() || outputKey == null || outputKey.isEmpty()) {
             log.debug("empty key in element " + localName);
             return;
         }
 
-        if (v == null && matchValue == null) {
-            mTransformKeyMap.put(matchKey, k);
+        if (matchValue == null && outputValue == null) {
+            mTransformKeyMap.put(matchKey, outputKey);
         } else {
-            mTransformTagMap.put(new Tag(matchKey, matchValue), new Tag(k, v));
+            mTransformTagMap.put(new Tag(matchKey, matchValue), new Tag(outputKey, outputValue));
         }
     }