diff --git a/kernel/trunk/core/heap.inc b/kernel/trunk/core/heap.inc
index 3a87383921..8319e1726c 100644
--- a/kernel/trunk/core/heap.inc
+++ b/kernel/trunk/core/heap.inc
@@ -138,8 +138,11 @@ proc init_kernel_heap
            mov [ebx+list_bk], eax
            mov [ebx+block_base], HEAP_BASE+4096*MEM_BLOCK_SIZE
 
-           mov ecx, [MEM_AMOUNT]
-           sub ecx, (HEAP_BASE - OS_BASE + 4096*MEM_BLOCK_SIZE)
+           mov ecx, [pg_data.kernel_pages]
+           shl ecx, 12
+           neg ecx
+           add ecx, [MEM_AMOUNT]
+           sub ecx, 4096*MEM_BLOCK_SIZE
            mov [heap_size], ecx
            mov [heap_free], ecx
            mov [ebx+block_size], ecx
diff --git a/kernel/trunk/init.inc b/kernel/trunk/init.inc
index 6bc82e61d6..274dcf7222 100644
--- a/kernel/trunk/init.inc
+++ b/kernel/trunk/init.inc
@@ -43,7 +43,6 @@ proc init_mem
            mov [pg_data.mem_amount-OS_BASE], eax
 
            shr eax, 12
-           mov edx, eax
            mov [pg_data.pages_count-OS_BASE], eax
            shr eax, 3
            mov [pg_data.pagemap_size-OS_BASE], eax
@@ -52,15 +51,7 @@ proc init_mem
            and eax, not 4095
            mov [tmp_page_tabs], eax
 
-           cmp edx, (OS_BASE/4096)
-           jbe @F
-           mov edx, (OS_BASE/4096)
-           jmp .set
-@@:
-           cmp edx, (HEAP_MIN_SIZE/4096)
-           jae .set
-           mov edx, (HEAP_MIN_SIZE/4096)
-.set:
+           mov edx, (((sys_pgmap-OS_BASE) + 0xFFFFFF) and not 0xFFFFFF) shr 12
            mov [pg_data.kernel_pages-OS_BASE], edx
            shr edx, 10
            mov [pg_data.kernel_tables-OS_BASE], edx