diff --git a/src/file_gm6.c b/src/file_gm6.c
index 4445a6cc..cc3f83bd 100644
--- a/src/file_gm6.c
+++ b/src/file_gm6.c
@@ -31,6 +31,7 @@
 #include "types.h"
 #include "filegen.h"
 
+/*@ requires \valid(file_stat); */
 static void register_header_check_gm6(file_stat_t *file_stat);
 
 const file_hint_t file_hint_gm6= {
@@ -43,6 +44,17 @@ const file_hint_t file_hint_gm6= {
 };
 
 //Version 8.1 file (.gm81)
+/*@
+  @ 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_gm6, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures \result == 0 || \result == 1;
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_gm81(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);
@@ -51,6 +63,17 @@ static int header_check_gm81(const unsigned char *buffer, const unsigned int buf
 }
 
 //Version 7.0-8.0 file (.gmk)
+/*@
+  @ 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_gm6, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures \result == 0 || \result == 1;
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_gmk(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);
@@ -59,6 +82,17 @@ static int header_check_gmk(const unsigned char *buffer, const unsigned int buff
 }
 
 //Version 6.0-6.1 file (.gm6)
+/*@
+  @ 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_gm6, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures \result == 0 || \result == 1;
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_gm6(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);
@@ -67,6 +101,17 @@ static int header_check_gm6(const unsigned char *buffer, const unsigned int buff
 }
 
 //Version 4.3-5.3A file (.gmd)
+/*@
+  @ 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_gm6, buffer+(..), file_recovery, file_recovery_new);
+  @ ensures \result == 0 || \result == 1;
+  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
+  @*/
 static int header_check_gmd(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);