diff --git a/CHANGELOG b/CHANGELOG
index cb7fe5e..a88b262 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,7 @@
+*SVN*
+
+* Ensure that an Ajax.Request's parameters option can be a Hash.  Closes #10172.  [kangax, sam] 
+
 * Ensure no comment nodes are returned in Selector queries (IE improperly returns comment nodes on getElementsByTagName("*")). Change Element#descendants to use Element#getElementsBySelector in order to avoid this issue. Closes #10220. [Jeff Gobel, Andrew Dupont]
 
 * Re-enable the XPath approach in Selector for Safari 3. Falls back to the non-XPath version when it sees a problematic token. [Andrew Dupont]
diff --git a/src/ajax.js b/src/ajax.js
index 0ecec59..dc1aa99 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -58,8 +58,11 @@ Ajax.Base = Class.create({
     Object.extend(this.options, options || { });
     
     this.options.method = this.options.method.toLowerCase();
+    
     if (Object.isString(this.options.parameters)) 
       this.options.parameters = this.options.parameters.toQueryParams();
+    else if (Object.isHash(this.options.parameters))
+      this.options.parameters = this.options.parameters.toObject();
   }
 });
 
diff --git a/test/unit/ajax.html b/test/unit/ajax.html
index 0de88a0..7cf836f 100644
--- a/test/unit/ajax.html
+++ b/test/unit/ajax.html
@@ -389,7 +389,22 @@
           parameters: { 'X-TEST': 'some value' },
           onComplete: function(transport) {
             assertEqual('some value', transport.getHeader('X-Test'));
-            assertNull(null, transport.getHeader('X-Inexistant'));
+            assertNull(transport.getHeader('X-Inexistant'));
+          }
+        }));
+      } else {
+        info(message);
+      }
+    }},
+    
+    testParametersCanBeHash: function() {with(this) {
+      if (isRunningFromRake) {
+        new Ajax.Request("/response", extendDefault({
+          parameters: $H({ "one": "two", "three": "four" }),
+          onComplete: function(transport) {
+            assertEqual("two", transport.getHeader("one"));
+            assertEqual("four", transport.getHeader("three"));
+            assertNull(transport.getHeader("toObject"));
           }
         }));
       } else {