diff --git a/dll/win32/kernel32/client/file/disk.c b/dll/win32/kernel32/client/file/disk.c
index 12751c6b1ad..8a09de7e180 100644
--- a/dll/win32/kernel32/client/file/disk.c
+++ b/dll/win32/kernel32/client/file/disk.c
@@ -237,12 +237,12 @@ GetDiskFreeSpaceW(IN LPCWSTR lpRootPathName,
     /* If we're to overflow output, make sure we return the maximum */
     if (FileFsSize.TotalAllocationUnits.HighPart != 0)
     {
-        FileFsSize.TotalAllocationUnits.LowPart = -1;
+        FileFsSize.TotalAllocationUnits.LowPart = MAXLONG;
     }
 
     if (FileFsSize.AvailableAllocationUnits.HighPart != 0)
     {
-        FileFsSize.AvailableAllocationUnits.LowPart = -1;
+        FileFsSize.AvailableAllocationUnits.LowPart = MAXLONG;
     }
 
     /* Return what user asked for */
@@ -268,7 +268,7 @@ GetDiskFreeSpaceW(IN LPCWSTR lpRootPathName,
             DWORD FreeClusters;
 
             /* Compute how many clusters there are in less than 2GB: 2 * 1024 * 1024 * 1024- 1 */
-            FreeClusters = 0x7FFFFFFF / (FileFsSize.SectorsPerAllocationUnit * FileFsSize.BytesPerSector);
+            FreeClusters = MAXLONG / (FileFsSize.SectorsPerAllocationUnit * FileFsSize.BytesPerSector);
             /* If that's higher than what was queried, then return the queried value, it's OK! */
             if (FreeClusters > FileFsSize.AvailableAllocationUnits.LowPart)
             {
@@ -291,7 +291,7 @@ GetDiskFreeSpaceW(IN LPCWSTR lpRootPathName,
             DWORD TotalClusters;
 
             /* Compute how many clusters there are in less than 2GB: 2 * 1024 * 1024 * 1024- 1 */
-            TotalClusters = 0x7FFFFFFF / (FileFsSize.SectorsPerAllocationUnit * FileFsSize.BytesPerSector);
+            TotalClusters = MAXLONG / (FileFsSize.SectorsPerAllocationUnit * FileFsSize.BytesPerSector);
             /* If that's higher than what was queried, then return the queried value, it's OK! */
             if (TotalClusters > FileFsSize.TotalAllocationUnits.LowPart)
             {
@@ -348,7 +348,7 @@ GetDiskFreeSpaceExW(IN LPCWSTR lpDirectoryName OPTIONAL,
     NTSTATUS Status;
     HANDLE RootHandle;
     UNICODE_STRING FileName;
-    DWORD BytesPerAllocationUnit;
+    DWORDLONG BytesPerAllocationUnit;
     IO_STATUS_BLOCK IoStatusBlock;
     OBJECT_ATTRIBUTES ObjectAttributes;
     FILE_FS_SIZE_INFORMATION FileFsSize;
@@ -407,21 +407,25 @@ GetDiskFreeSpaceExW(IN LPCWSTR lpDirectoryName OPTIONAL,
             NtClose(RootHandle);
 
             /* Compute the size of an AU */
-            BytesPerAllocationUnit = FileFsFullSize.SectorsPerAllocationUnit * FileFsFullSize.BytesPerSector;
+            BytesPerAllocationUnit = UInt32x32To64(FileFsFullSize.SectorsPerAllocationUnit,
+                                                   FileFsFullSize.BytesPerSector);
 
             /* And then return what was asked */
             if (lpFreeBytesAvailableToCaller != NULL)
             {
-                lpFreeBytesAvailableToCaller->QuadPart = FileFsFullSize.CallerAvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
+                lpFreeBytesAvailableToCaller->QuadPart =
+                    FileFsFullSize.CallerAvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
             }
 
             if (lpTotalNumberOfBytes != NULL)
             {
-                lpTotalNumberOfBytes->QuadPart = FileFsFullSize.TotalAllocationUnits.QuadPart * BytesPerAllocationUnit;
+                lpTotalNumberOfBytes->QuadPart =
+                    FileFsFullSize.TotalAllocationUnits.QuadPart * BytesPerAllocationUnit;
             }
 
             /* No need to check for nullness ;-) */
-            lpTotalNumberOfFreeBytes->QuadPart = FileFsFullSize.ActualAvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
+            lpTotalNumberOfFreeBytes->QuadPart =
+                FileFsFullSize.ActualAvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
 
             return TRUE;
         }
@@ -439,22 +443,26 @@ GetDiskFreeSpaceExW(IN LPCWSTR lpDirectoryName OPTIONAL,
     }
 
     /* Compute the size of an AU */
-    BytesPerAllocationUnit = FileFsSize.SectorsPerAllocationUnit * FileFsSize.BytesPerSector;
+    BytesPerAllocationUnit =
+        UInt32x32To64(FileFsSize.SectorsPerAllocationUnit, FileFsSize.BytesPerSector);
 
     /* And then return what was asked, available is free, the same! */
     if (lpFreeBytesAvailableToCaller != NULL)
     {
-        lpFreeBytesAvailableToCaller->QuadPart = FileFsSize.AvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
+        lpFreeBytesAvailableToCaller->QuadPart =
+            FileFsSize.AvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
     }
 
     if (lpTotalNumberOfBytes != NULL)
     {
-        lpTotalNumberOfBytes->QuadPart = FileFsSize.TotalAllocationUnits.QuadPart * BytesPerAllocationUnit;
+        lpTotalNumberOfBytes->QuadPart =
+            FileFsSize.TotalAllocationUnits.QuadPart * BytesPerAllocationUnit;
     }
 
     if (lpTotalNumberOfFreeBytes != NULL)
     {
-        lpTotalNumberOfFreeBytes->QuadPart = FileFsSize.AvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
+        lpTotalNumberOfFreeBytes->QuadPart =
+            FileFsSize.AvailableAllocationUnits.QuadPart * BytesPerAllocationUnit;
     }
 
     return TRUE;