diff --git a/src/main/java/org/scribe/extractors/BaseStringExtractorImpl.java b/src/main/java/org/scribe/extractors/BaseStringExtractorImpl.java
index f18c62c..ebaf20a 100644
--- a/src/main/java/org/scribe/extractors/BaseStringExtractorImpl.java
+++ b/src/main/java/org/scribe/extractors/BaseStringExtractorImpl.java
@@ -32,11 +32,11 @@ public class BaseStringExtractorImpl implements BaseStringExtractor
   private String getSortedAndEncodedParams(OAuthRequest request)
   {
     Map<String, String> params = new HashMap<String, String>();
-    params.putAll(request.getQueryStringParams());
-    params.putAll(request.getBodyParams());
-    params.putAll(request.getOauthParameters());
+    MapUtils.decodeAndAppendEntries(request.getQueryStringParams(), params);
+    MapUtils.decodeAndAppendEntries(request.getBodyParams(), params);
+    MapUtils.decodeAndAppendEntries(request.getOauthParameters(), params);
     params = MapUtils.sort(params);
-    return URLUtils.percentEncode(URLUtils.formURLEncodeMap(params));
+    return URLUtils.percentEncode(URLUtils.concatSortedPercentEncodedParams(params));
   }
 
   private void checkPreconditions(OAuthRequest request)
diff --git a/src/main/java/org/scribe/utils/MapUtils.java b/src/main/java/org/scribe/utils/MapUtils.java
index db08db3..a77e4b6 100644
--- a/src/main/java/org/scribe/utils/MapUtils.java
+++ b/src/main/java/org/scribe/utils/MapUtils.java
@@ -33,4 +33,19 @@ public class MapUtils
     Collections.sort(keys);
     return keys;
   }
+
+  /**
+   * Form-urlDecodes and appends all keys from the source {@link Map} to the
+   * target {@link Map}
+   *
+   * @param source Map from where the keys get copied and decoded
+   * @param target Map where the decoded keys are copied to
+   */
+  public static void decodeAndAppendEntries(Map<String, String> source, Map<String, String> target)
+  {
+    for (String key: source.keySet())
+    {
+      target.put(URLUtils.percentEncode(key), URLUtils.percentEncode(source.get(key)));
+    }
+  }
 }
diff --git a/src/main/java/org/scribe/utils/URLUtils.java b/src/main/java/org/scribe/utils/URLUtils.java
index 8c6f492..eb82e46 100644
--- a/src/main/java/org/scribe/utils/URLUtils.java
+++ b/src/main/java/org/scribe/utils/URLUtils.java
@@ -139,6 +139,7 @@ public class URLUtils
    * @param params key-value map
    * @return querystring-like String
    */
+  // TODO Move to MapUtils
   public static String concatSortedPercentEncodedParams(Map<String, String> params)
   {
     StringBuilder result = new StringBuilder();
@@ -156,6 +157,7 @@ public class URLUtils
    * @param queryString querystring-like String
    * @return a map with the form-urldecoded parameters
    */
+  // TODO Move to MapUtils
   public static Map<String, String> queryStringToMap(String queryString)
   {
     Map<String, String> result = new HashMap<String, String>();