diff --git a/dlls/kernel32/tests/heap.c b/dlls/kernel32/tests/heap.c
index fead409960c..59a82c0c579 100644
--- a/dlls/kernel32/tests/heap.c
+++ b/dlls/kernel32/tests/heap.c
@@ -578,7 +578,6 @@ static void test_HeapCreate(void)
     todo_wine
     ok( entries[0].Region.dwCommittedSize == 0x400 * sizeof(void *),
         "got Region.dwCommittedSize %#lx\n", entries[0].Region.dwCommittedSize );
-    todo_wine
     ok( entries[0].Region.dwUnCommittedSize == 0x10000 - entries[0].Region.dwCommittedSize ||
         entries[0].Region.dwUnCommittedSize == 0x10000 * sizeof(void *) - entries[0].Region.dwCommittedSize /* win7 */,
         "got Region.dwUnCommittedSize %#lx\n", entries[0].Region.dwUnCommittedSize );
@@ -3019,9 +3018,9 @@ static void test_block_layout( HANDLE heap, DWORD global_flags, DWORD heap_flags
         expect_size = max( alloc_size, 2 * sizeof(void *) );
         expect_size = ALIGN_BLOCK_SIZE( expect_size + extra_size );
         diff = min( llabs( ptr2 - ptr1 ), llabs( ptr1 - ptr0 ) );
-        todo_wine_if( (!(global_flags & ~FLG_HEAP_ENABLE_FREE_CHECK) && alloc_size < 2 * sizeof(void *)) )
+        todo_wine_if( (!global_flags && alloc_size < 2 * sizeof(void *)) ||
+                      ((heap_flags & HEAP_FREE_CHECKING_ENABLED) && diff >= 0x100000) )
         ok( diff == expect_size, "got diff %#Ix exp %#Ix\n", diff, expect_size );
-
         ok( !memcmp( ptr0 + alloc_size, tail_buf, tail_size ), "missing block tail\n" );
         ok( !memcmp( ptr1 + alloc_size, tail_buf, tail_size ), "missing block tail\n" );
         ok( !memcmp( ptr2 + alloc_size, tail_buf, tail_size ), "missing block tail\n" );
@@ -3661,7 +3660,6 @@ static void test_heap_size( SIZE_T initial_size )
     heap = HeapCreate( HEAP_NO_SERIALIZE, initial_size, 0 );
     get_valloc_info( heap, &current_base, &alloc_size );
 
-    todo_wine
     ok( alloc_size == initial_size + default_heap_size || broken( (initial_size && alloc_size == initial_size)
         || (!initial_size && (alloc_size == default_heap_size * sizeof(void*))) ) /* Win7 */,
         "got %#Ix.\n", alloc_size );
@@ -3687,11 +3685,9 @@ static void test_heap_size( SIZE_T initial_size )
                     max_size_reached = TRUE;
             }
         }
-        todo_wine_if( !initial_subheap )
         ok( alloc_size == current_subheap_size, "got %#Ix.\n", alloc_size );
         winetest_pop_context();
     }
-    todo_wine_if( sizeof(void *) == 8 )
     ok( max_size_reached, "Did not reach maximum subheap size.\n" );
 
     HeapDestroy( heap );
diff --git a/dlls/ntdll/heap.c b/dlls/ntdll/heap.c
index ce3419734ee..bbb4cbf8a99 100644
--- a/dlls/ntdll/heap.c
+++ b/dlls/ntdll/heap.c
@@ -311,7 +311,12 @@ C_ASSERT( offsetof(struct heap, subheap) <= REGION_ALIGN - 1 );
 
 #define HEAP_MAGIC       ((DWORD)('H' | ('E'<<8) | ('A'<<16) | ('P'<<24)))
 
-#define HEAP_DEF_SIZE        (0x40000 * BLOCK_ALIGN)
+#define HEAP_INITIAL_SIZE      0x10000
+#define HEAP_INITIAL_GROW_SIZE 0x100000
+#define HEAP_MAX_GROW_SIZE     0xfd0000
+
+C_ASSERT( HEAP_MIN_LARGE_BLOCK_SIZE <= HEAP_INITIAL_GROW_SIZE );
+
 #define MAX_FREE_PENDING     1024    /* max number of free requests to delay */
 
 /* some undocumented flags (names are made up) */
@@ -1133,7 +1138,7 @@ static struct block *find_free_block( struct heap *heap, ULONG flags, SIZE_T blo
 
     if ((subheap = create_subheap( heap, flags, max( heap->grow_size, total_size ), total_size )))
     {
-        if (heap->grow_size <= HEAP_MAX_FREE_BLOCK_SIZE / 2) heap->grow_size *= 2;
+        heap->grow_size = min( heap->grow_size * 2, HEAP_MAX_GROW_SIZE );
     }
     else while (!subheap)  /* shrink the grow size again if we are running out of space */
     {
@@ -1517,7 +1522,7 @@ HANDLE WINAPI RtlCreateHeap( ULONG flags, void *addr, SIZE_T total_size, SIZE_T
     flags &= ~(HEAP_TAIL_CHECKING_ENABLED|HEAP_FREE_CHECKING_ENABLED);
     if (process_heap) flags |= HEAP_PRIVATE;
     if (!process_heap || !total_size || (flags & HEAP_SHARED)) flags |= HEAP_GROWABLE;
-    if (!total_size) total_size = HEAP_DEF_SIZE;
+    if (!total_size) total_size = commit_size + HEAP_INITIAL_SIZE;
 
     if (!(heap = addr))
     {
@@ -1532,7 +1537,7 @@ HANDLE WINAPI RtlCreateHeap( ULONG flags, void *addr, SIZE_T total_size, SIZE_T
     heap->flags         = (flags & ~HEAP_SHARED);
     heap->compat_info   = HEAP_STD;
     heap->magic         = HEAP_MAGIC;
-    heap->grow_size     = max( HEAP_DEF_SIZE, total_size );
+    heap->grow_size     = HEAP_INITIAL_GROW_SIZE;
     heap->min_size      = commit_size;
     list_init( &heap->subheap_list );
     list_init( &heap->large_list );