diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 1de2094d2e57..a34c785c5a63 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -274,7 +274,7 @@ static inline int is_new_memtype_allowed(u64 paddr, unsigned long size,
 	/*
 	 * PAT type is always WB for untracked ranges, so no need to check.
 	 */
-	if (x86_platform.is_untracked_pat_range(paddr, paddr + size - 1))
+	if (x86_platform.is_untracked_pat_range(paddr, paddr + size))
 		return 1;
 
 	/*
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 38a66ef9426d..b5bc08cfcea6 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -394,7 +394,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 	}
 
 	/* Low ISA region is always mapped WB in page table. No need to track */
-	if (x86_platform.is_untracked_pat_range(start, end - 1)) {
+	if (x86_platform.is_untracked_pat_range(start, end)) {
 		if (new_type)
 			*new_type = _PAGE_CACHE_WB;
 		return 0;
@@ -505,7 +505,7 @@ int free_memtype(u64 start, u64 end)
 		return 0;
 
 	/* Low ISA region is always mapped WB. No need to track */
-	if (x86_platform.is_untracked_pat_range(start, end - 1))
+	if (x86_platform.is_untracked_pat_range(start, end))
 		return 0;
 
 	is_range_ram = pat_pagerange_is_ram(start, end);
@@ -588,7 +588,7 @@ static unsigned long lookup_memtype(u64 paddr)
 	int rettype = _PAGE_CACHE_WB;
 	struct memtype *entry;
 
-	if (x86_platform.is_untracked_pat_range(paddr, paddr + PAGE_SIZE - 1))
+	if (x86_platform.is_untracked_pat_range(paddr, paddr + PAGE_SIZE))
 		return rettype;
 
 	if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {