diff --git a/src/file_fit.c b/src/file_fit.c
index 3a1d3176..defe6a66 100644
--- a/src/file_fit.c
+++ b/src/file_fit.c
@@ -33,6 +33,7 @@
 #include "filegen.h"
 #include "common.h"
 
+/*@ requires \valid(file_stat); */
 static void register_header_check_fit(file_stat_t *file_stat);
 
 const file_hint_t file_hint_fit = {
@@ -53,6 +54,17 @@ struct fits_header
     char signature[4];
 } __attribute__ ((gcc_struct, __packed__));
 
+/*@
+  @ requires buffer_size >= sizeof(struct fits_header);
+  @ 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_fit, 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_fit(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)
 {
   const struct fits_header* h = (const struct fits_header *)buffer;