diff --git a/JavaScriptCore/ChangeLog b/JavaScriptCore/ChangeLog
index c2a309f1becbeab48728052680ddc64e4a6d5333..7bf883245deb4482c0383e14a8200020ee2bbaac 100644
--- a/JavaScriptCore/ChangeLog
+++ b/JavaScriptCore/ChangeLog
@@ -1,3 +1,16 @@
+2009-08-12  Ada Chan  <adachan@apple.com>
+
+        Added workaround for the limitation that VirtualFree with MEM_RELEASE
+        can only accept the base address returned by VirtualAlloc when the region
+        was reserved and it can only free the entire region, and not a part of it.
+
+        Reviewed by Oliver Hunt.
+
+        * runtime/MarkStack.h:
+        (JSC::MarkStack::MarkStackArray::shrinkAllocation):
+        * runtime/MarkStackWin.cpp:
+        (JSC::MarkStack::releaseStack):
+
 2009-08-12  Balazs Kelemen  <kelemen.balazs.3@stud.u-szeged.hu>
 
         Reviewed by Ariya Hidayat.
diff --git a/JavaScriptCore/runtime/MarkStack.h b/JavaScriptCore/runtime/MarkStack.h
index 7a7b3afb5c3afb0e3fa6046048980243e65c98bb..ee537959d68cd16ee8a6037f964989daa8bd2ec8 100644
--- a/JavaScriptCore/runtime/MarkStack.h
+++ b/JavaScriptCore/runtime/MarkStack.h
@@ -150,7 +150,14 @@ namespace JSC {
                 ASSERT(0 == (size % MarkStack::pageSize()));
                 if (size == m_allocated)
                     return;
+#if PLATFORM(WIN)
+                // We cannot release a part of a region with VirtualFree.  To get around this,
+                // we'll release the entire region and reallocate the size that we want.
+                releaseStack(m_data, m_allocated);
+                m_data = reinterpret_cast<T*>(allocateStack(size));
+#else
                 releaseStack(reinterpret_cast<char*>(m_data) + size, m_allocated - size);
+#endif
                 m_allocated = size;
                 m_capacity = m_allocated / sizeof(T);
             }
diff --git a/JavaScriptCore/runtime/MarkStackWin.cpp b/JavaScriptCore/runtime/MarkStackWin.cpp
index dbc330692810c05c5e7395d5b7f0228da046b00d..1fdd06a655c370dfbc9e0da041b0871f31ab0029 100644
--- a/JavaScriptCore/runtime/MarkStackWin.cpp
+++ b/JavaScriptCore/runtime/MarkStackWin.cpp
@@ -43,9 +43,11 @@ void* MarkStack::allocateStack(size_t size)
 {
     return VirtualAlloc(0, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
 }
-void MarkStack::releaseStack(void* addr, size_t size)
+void MarkStack::releaseStack(void* addr, size_t)
 {
-    VirtualFree(addr, size, MEM_RELEASE);
+    // According to http://msdn.microsoft.com/en-us/library/aa366892(VS.85).aspx,
+    // dwSize must be 0 if dwFreeType is MEM_RELEASE.
+    VirtualFree(addr, 0, MEM_RELEASE);
 }
 
 }