diff --git a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/FlattenerUtils.java b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/FlattenerUtils.java
index d45014f..0f7e6ed 100644
--- a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/FlattenerUtils.java
+++ b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/FlattenerUtils.java
@@ -9,7 +9,10 @@ public static String filter(String string, String regexpFilter) {
     return string.replaceAll(regexpFilter, "");
   }
 
-  public static String noWhitespace(String mixedString) {
-    return mixedString.replaceAll("\\s", "_");
+  public static String toVariableName(String mixedString) {
+    if (mixedString == null) {
+      return null;
+    }
+    return mixedString.replaceAll("\\s", "_").replaceAll("-", "_");
   }
 }
diff --git a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/JsonFlattener.java b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/JsonFlattener.java
index a51f6ba..b672971 100644
--- a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/JsonFlattener.java
+++ b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/JsonFlattener.java
@@ -2,7 +2,7 @@
 
 import static com.google.common.collect.Maps.newHashMap;
 import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.filter;
-import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.noWhitespace;
+import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.toVariableName;
 
 import java.util.List;
 import java.util.Map;
@@ -26,7 +26,7 @@ public Map<String, String> flatternJson(String key, String regexFilter, Object r
             flatternJson(key + "_" + entry.getKey(), regexFilter, entry.getValue()));
       }
     } else if (resolved != null) {
-      String noWhitespaces = noWhitespace(key);
+      String noWhitespaces = toVariableName(key);
       resolvedVariables.put(noWhitespaces, filter(resolved.toString(), regexFilter));
     }
     return resolvedVariables;
diff --git a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestHeaderResolver.java b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestHeaderResolver.java
index 59f5850..d0a36e8 100644
--- a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestHeaderResolver.java
+++ b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestHeaderResolver.java
@@ -3,13 +3,13 @@
 import static com.google.common.base.Optional.absent;
 import static com.google.common.base.Optional.of;
 import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.filter;
+import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.toVariableName;
 
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import org.apache.commons.lang.StringUtils;
 import org.jenkinsci.plugins.gwt.GenericHeaderVariable;
 
 import com.google.common.base.Optional;
@@ -33,11 +33,11 @@ public Map<String, String> getRequestHeaders(
         String headerValue = headerEnumeration.nextElement();
         String regexpFilter = configuredVariable.get().getRegexpFilter();
         String filteredValue = filter(headerValue, regexpFilter);
-        found.put(StringUtils.replace(headerName, "-", "_") + "_" + i, filteredValue);
+        found.put(toVariableName(headerName) + "_" + i, filteredValue);
         boolean firstAndOnlyValue = i == 0 && !headerEnumeration.hasMoreElements();
         if (firstAndOnlyValue) {
           //Users will probably expect this variable for parameters that are never a list
-          found.put(StringUtils.replace(headerName, "-", "_"), filteredValue);
+          found.put(toVariableName(headerName), filteredValue);
         }
         i++;
       }
diff --git a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestParameterResolver.java b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestParameterResolver.java
index 22e88b0..6e30796 100644
--- a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestParameterResolver.java
+++ b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/RequestParameterResolver.java
@@ -3,6 +3,7 @@
 import static com.google.common.base.Optional.absent;
 import static com.google.common.collect.Maps.newHashMap;
 import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.filter;
+import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.toVariableName;
 
 import java.util.List;
 import java.util.Map;
@@ -28,11 +29,11 @@ public Map<String, String> getRequestParameters(
         String[] values = incomingParameterMap.get(requestParamName);
         for (int i = 0; i < values.length; i++) {
           String filteredValue = filter(values[i], configuredVariable.get().getRegexpFilter());
-          resolvedVariables.put(requestParamName + "_" + i, filteredValue);
+          resolvedVariables.put(toVariableName(requestParamName) + "_" + i, filteredValue);
           boolean firstAndOnlyValue = i == 0 && values.length == 1;
           if (firstAndOnlyValue) {
             //Users will probably expect this variable for parameters that are never a list
-            resolvedVariables.put(requestParamName, filteredValue);
+            resolvedVariables.put(toVariableName(requestParamName), filteredValue);
           }
         }
       }
diff --git a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/XmlFlattener.java b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/XmlFlattener.java
index bedde91..9874354 100644
--- a/src/main/java/org/jenkinsci/plugins/gwt/resolvers/XmlFlattener.java
+++ b/src/main/java/org/jenkinsci/plugins/gwt/resolvers/XmlFlattener.java
@@ -2,7 +2,7 @@
 
 import static com.google.common.collect.Maps.newHashMap;
 import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.filter;
-import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.noWhitespace;
+import static org.jenkinsci.plugins.gwt.resolvers.FlattenerUtils.toVariableName;
 
 import java.util.Map;
 
@@ -31,7 +31,7 @@ private Map<String, String> flattenXmlNode(
       String parentKey, String regexFilter, Node node, int level, boolean fromRootLevel) {
     Map<String, String> resolvedVariables = newHashMap();
     if (isXmlLeafNode(node)) {
-      String noWhitespaces = noWhitespace(parentKey);
+      String noWhitespaces = toVariableName(parentKey);
       resolvedVariables.put(noWhitespaces, filter(node.getTextContent(), regexFilter));
     } else {
       for (int i = 0; i < node.getChildNodes().getLength(); i++) {
@@ -39,7 +39,7 @@ private Map<String, String> flattenXmlNode(
         String childKey =
             expandKey(parentKey, level, fromRootLevel) + "_" + childNode.getNodeName();
         if (isXmlLeafNode(childNode)) {
-          String noWhitespace = noWhitespace(childKey);
+          String noWhitespace = toVariableName(childKey);
           resolvedVariables.put(noWhitespace, filter(childNode.getTextContent(), regexFilter));
         } else {
           //leafnode and text inside leafnode are 2 nodes, so /2 to keep counter in line