diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 6ab3196..10b5230 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -614,7 +614,7 @@
 	 */
 	offset = phys_addr & ~PAGE_MASK;
 	phys_addr &= PAGE_MASK;
-	size = PAGE_ALIGN(last_addr) - phys_addr;
+	size = PAGE_ALIGN(last_addr + 1) - phys_addr;
 
 	/*
 	 * Mappings have to fit in the FIX_BTMAP area.