diff --git a/src/file_wks.c b/src/file_wks.c
index 82e3a2aa..2159a346 100644
--- a/src/file_wks.c
+++ b/src/file_wks.c
@@ -31,15 +31,16 @@
 #include "types.h"
 #include "filegen.h"
 
+/*@ requires \valid(file_stat); */
 static void register_header_check_wks(file_stat_t *file_stat);
 
-const file_hint_t file_hint_wks= {
-  .extension="wks",
-  .description="Lotus 1-2-3",
-  .max_filesize=PHOTOREC_MAX_FILE_SIZE,
-  .recover=1,
-  .enable_by_default=1,
-  .register_header_check=&register_header_check_wks
+const file_hint_t file_hint_wks = {
+  .extension = "wks",
+  .description = "Lotus 1-2-3",
+  .max_filesize = PHOTOREC_MAX_FILE_SIZE,
+  .recover = 1,
+  .enable_by_default = 1,
+  .register_header_check = &register_header_check_wks
 };
 
 /*
@@ -53,26 +54,46 @@ const file_hint_t file_hint_wks= {
  * http://www.schnarff.com/file-formats/lotus-1-2-3/WSFF1.TXT
  * http://www.schnarff.com/file-formats/lotus-1-2-3/WSFF2.TXT
  */
+/*@
+  @ requires buffer_size > 0;
+  @ requires \valid_read(buffer+(0..buffer_size-1));
+  @ requires valid_file_recovery(file_recovery);
+  @ requires \valid(file_recovery_new);
+  @ requires file_recovery_new->blocksize > 0;
+  @ requires separation: \separated(&file_hint_wks, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_wk4(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
 {
   reset_file_recovery(file_recovery_new);
-  file_recovery_new->extension="wk4";
+  file_recovery_new->extension = "wk4";
   return 1;
 }
 
+/*@
+  @ requires buffer_size > 0;
+  @ requires \valid_read(buffer+(0..buffer_size-1));
+  @ requires valid_file_recovery(file_recovery);
+  @ requires \valid(file_recovery_new);
+  @ requires file_recovery_new->blocksize > 0;
+  @ requires separation: \separated(&file_hint_wks, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_wks(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
 {
   reset_file_recovery(file_recovery_new);
-  file_recovery_new->extension=file_hint_wks.extension;
+  file_recovery_new->extension = file_hint_wks.extension;
   return 1;
 }
 
 static void register_header_check_wks(file_stat_t *file_stat)
 {
-  static const unsigned char wks_header[10]  = { 0x00, 0x00, 0x02, 0x00, 0x04, 0x04,
-    0x06, 0x00, 0x08, 0x00};
-  static const unsigned char wk4_header[8]  = { 0x00, 0x00, 0x1a, 0x00, 0x02, 0x10, 0x04, 0x00};
-  register_header_check(0, wks_header,sizeof(wks_header), &header_check_wks, file_stat);
-  register_header_check(0, wk4_header,sizeof(wk4_header), &header_check_wk4, file_stat);
+  static const unsigned char wks_header[10] = { 0x00, 0x00, 0x02, 0x00, 0x04, 0x04,
+                                                0x06, 0x00, 0x08, 0x00 };
+  static const unsigned char wk4_header[8] = { 0x00, 0x00, 0x1a, 0x00, 0x02, 0x10, 0x04, 0x00 };
+  register_header_check(0, wks_header, sizeof(wks_header), &header_check_wks, file_stat);
+  register_header_check(0, wk4_header, sizeof(wk4_header), &header_check_wk4, file_stat);
 }
 #endif