Index: lib/sanitizer_common/sanitizer_allocator.h
===================================================================
--- lib/sanitizer_common/sanitizer_allocator.h
+++ lib/sanitizer_common/sanitizer_allocator.h
@@ -421,7 +421,8 @@
 
   // Test-only.
   void TestOnlyUnmap() {
-    UnmapWithCallback(SpaceBeg(), kSpaceSize + AdditionalSize());
+    UnmapWithCallback(SpaceBeg(), kSpaceSize);
+    UnmapWithCallback(SpaceEnd(), AdditionalSize());
   }
 
   void PrintStats() {
Index: lib/sanitizer_common/sanitizer_win.cc
===================================================================
--- lib/sanitizer_common/sanitizer_win.cc
+++ lib/sanitizer_common/sanitizer_win.cc
@@ -183,7 +183,10 @@
 
 void *MmapFixedOrDie(uptr fixed_addr, uptr size) {
   void *p = VirtualAlloc((LPVOID)fixed_addr, size,
-      MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
+      MEM_COMMIT, PAGE_READWRITE);
+  if (p == 0)
+    p = VirtualAlloc((LPVOID)fixed_addr, size,
+        MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
   if (p == 0) {
     char mem_type[30];
     internal_snprintf(mem_type, sizeof(mem_type), "memory at address 0x%zx",
@@ -201,7 +204,7 @@
 void *MmapFixedNoAccess(uptr fixed_addr, uptr size, const char *name) {
   (void)name; // unsupported
   void *res = VirtualAlloc((LPVOID)fixed_addr, size,
-                           MEM_RESERVE | MEM_COMMIT, PAGE_NOACCESS);
+                           MEM_RESERVE, PAGE_NOACCESS);
   if (res == 0)
     Report("WARNING: %s failed to "
            "mprotect %p (%zd) bytes at %p (error code: %d)\n",
Index: lib/sanitizer_common/tests/sanitizer_allocator_test.cc
===================================================================
--- lib/sanitizer_common/tests/sanitizer_allocator_test.cc
+++ lib/sanitizer_common/tests/sanitizer_allocator_test.cc
@@ -29,9 +29,9 @@
 #if !SANITIZER_DEBUG
 
 #if SANITIZER_CAN_USE_ALLOCATOR64
-static const uptr kAllocatorSpace = 0x700000000000ULL;
-static const uptr kAllocatorSize  = 0x010000000000ULL;  // 1T.
-static const u64 kAddressSpaceSize = 1ULL << 47;
+static const uptr kAllocatorSpace = 0x10000000000ULL;
+static const uptr kAllocatorSize  =  0x10000000000ULL;  // 1T.
+static const u64 kAddressSpaceSize = 1ULL << 40;
 
 typedef SizeClassAllocator64<
   kAllocatorSpace, kAllocatorSize, 16, DefaultSizeClassMap> Allocator64;
@@ -235,10 +235,12 @@
 TEST(SanitizerCommon, SizeClassAllocator64CompactGetBlockBegin) {
   SizeClassAllocatorGetBlockBeginStress<Allocator64Compact>();
 }
+#endif  // SANITIZER_CAN_USE_ALLOCATOR64
+
 TEST(SanitizerCommon, SizeClassAllocator32CompactGetBlockBegin) {
   SizeClassAllocatorGetBlockBeginStress<Allocator32Compact>();
 }
-#endif  // SANITIZER_CAN_USE_ALLOCATOR64
+
 
 struct TestMapUnmapCallback {
   static int map_count, unmap_count;
@@ -266,7 +268,8 @@
   a->AllocateBatch(&stats, &cache, 32);
   EXPECT_EQ(TestMapUnmapCallback::map_count, 3);  // State + alloc + metadata.
   a->TestOnlyUnmap();
-  EXPECT_EQ(TestMapUnmapCallback::unmap_count, 1);  // The whole thing.
+  // Expect unmapping of 'memory space' and 'additional memory'.
+  EXPECT_EQ(TestMapUnmapCallback::unmap_count, 2);
   delete a;
 }
 #endif