diff --git a/files/directory.c b/files/directory.c
index 3d81f69..9ef6efe 100644
--- a/files/directory.c
+++ b/files/directory.c
@@ -193,10 +193,18 @@
  */
 BYTE WINAPI GetTempDrive( BYTE ignored )
 {
-    char buffer[2];
+    char *buffer;
+    BYTE ret;
+    UINT32 len = GetTempPath32A( 0, NULL );
+
+    if (!(buffer = HeapAlloc( GetProcessHeap(), 0, len + 1 )) )
+      return DRIVE_GetCurrentDrive() + 'A';
+
     /* FIXME: apparently Windows does something with the ignored byte */
-    if (!GetTempPath32A( sizeof(buffer), buffer )) buffer[0] = 'C';
-    return toupper(buffer[0]);
+    if (!GetTempPath32A( len, buffer )) buffer[0] = 'C';
+    ret = buffer[0];
+    HeapFree( GetProcessHeap(), 0, buffer );
+    return toupper(ret);
 }