diff --git a/target-i386/arch_memory_mapping.c b/target-i386/arch_memory_mapping.c
index 844893f44d..24884bd482 100644
--- a/target-i386/arch_memory_mapping.c
+++ b/target-i386/arch_memory_mapping.c
@@ -75,6 +75,8 @@ static void walk_pte2(MemoryMappingList *list,
 }
 
 /* PAE Paging or IA-32e Paging */
+#define PLM4_ADDR_MASK 0xffffffffff000 /* selects bits 51:12 */
+
 static void walk_pde(MemoryMappingList *list, hwaddr pde_start_addr,
                      int32_t a20_mask, target_ulong start_line_addr)
 {
@@ -105,7 +107,7 @@ static void walk_pde(MemoryMappingList *list, hwaddr pde_start_addr,
             continue;
         }
 
-        pte_start_addr = (pde & ~0xfff) & a20_mask;
+        pte_start_addr = (pde & PLM4_ADDR_MASK) & a20_mask;
         walk_pte(list, pte_start_addr, a20_mask, line_addr);
     }
 }
@@ -208,7 +210,7 @@ static void walk_pdpe(MemoryMappingList *list,
             continue;
         }
 
-        pde_start_addr = (pdpe & ~0xfff) & a20_mask;
+        pde_start_addr = (pdpe & PLM4_ADDR_MASK) & a20_mask;
         walk_pde(list, pde_start_addr, a20_mask, line_addr);
     }
 }
@@ -231,7 +233,7 @@ static void walk_pml4e(MemoryMappingList *list,
         }
 
         line_addr = ((i & 0x1ffULL) << 39) | (0xffffULL << 48);
-        pdpe_start_addr = (pml4e & ~0xfff) & a20_mask;
+        pdpe_start_addr = (pml4e & PLM4_ADDR_MASK) & a20_mask;
         walk_pdpe(list, pdpe_start_addr, a20_mask, line_addr);
     }
 }
@@ -249,7 +251,7 @@ int cpu_get_memory_mapping(MemoryMappingList *list, CPUArchState *env)
         if (env->hflags & HF_LMA_MASK) {
             hwaddr pml4e_addr;
 
-            pml4e_addr = (env->cr[3] & ~0xfff) & env->a20_mask;
+            pml4e_addr = (env->cr[3] & PLM4_ADDR_MASK) & env->a20_mask;
             walk_pml4e(list, pml4e_addr, env->a20_mask);
         } else
 #endif