diff --git a/dlls/setupapi/misc.c b/dlls/setupapi/misc.c
index 3b5d62b682c..3b0c9477747 100644
--- a/dlls/setupapi/misc.c
+++ b/dlls/setupapi/misc.c
@@ -933,6 +933,8 @@ static BOOL find_existing_inf(const WCHAR *source, WCHAR *target)
             if (dest_file == INVALID_HANDLE_VALUE)
                 continue;
 
+            SetFilePointer( source_file, 0, NULL, FILE_BEGIN );
+
             if (GetFileSizeEx( dest_file, &dest_file_size )
                     && dest_file_size.QuadPart == source_file_size.QuadPart
                     && !compare_files( source_file, dest_file ))