diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
index 92753c7269..392aeb8a02 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
@@ -1135,10 +1135,6 @@ CoreConvertPagesWithGuard (
     OldPages = NumberOfPages;
 
     AdjustMemoryF (&Start, &NumberOfPages);
-    if (NumberOfPages == 0) {
-      return EFI_SUCCESS;
-    }
-
     //
     // It's safe to unset Guard page inside memory lock because there should
     // be no memory allocation occurred in updating memory page attribute at
@@ -1147,6 +1143,9 @@ CoreConvertPagesWithGuard (
     // marking it usable (from non-present to present).
     //
     UnsetGuardForMemory (OldStart, OldPages);
+    if (NumberOfPages == 0) {
+      return EFI_SUCCESS;
+    }
   } else {
     AdjustMemoryA (&Start, &NumberOfPages);
   }
diff --git a/MdeModulePkg/Core/Dxe/Mem/Pool.c b/MdeModulePkg/Core/Dxe/Mem/Pool.c
index df9a1d28df..1ff2061f7f 100644
--- a/MdeModulePkg/Core/Dxe/Mem/Pool.c
+++ b/MdeModulePkg/Core/Dxe/Mem/Pool.c
@@ -642,15 +642,15 @@ CoreFreePoolPagesWithGuard (
   NoPagesGuarded = NoPages;
 
   AdjustMemoryF (&Memory, &NoPages);
+  //
+  // It's safe to unset Guard page inside memory lock because there should
+  // be no memory allocation occurred in updating memory page attribute at
+  // this point. And unsetting Guard page before free will prevent Guard
+  // page just freed back to pool from being allocated right away before
+  // marking it usable (from non-present to present).
+  //
+  UnsetGuardForMemory (MemoryGuarded, NoPagesGuarded);
   if (NoPages > 0) {
-    //
-    // It's safe to unset Guard page inside memory lock because there should
-    // be no memory allocation occurred in updating memory page attribute at
-    // this point. And unsetting Guard page before free will prevent Guard
-    // page just freed back to pool from being allocated right away before
-    // marking it usable (from non-present to present).
-    //
-    UnsetGuardForMemory (MemoryGuarded, NoPagesGuarded);
     CoreFreePoolPagesI (PoolType, Memory, NoPages);
   }
 }