diff --git a/src/file_hm.c b/src/file_hm.c
index ea2f07cb..757b9723 100644
--- a/src/file_hm.c
+++ b/src/file_hm.c
@@ -31,27 +31,39 @@
 #include "types.h"
 #include "filegen.h"
 
+/*@ requires \valid(file_stat); */
 static void register_header_check_hm(file_stat_t *file_stat);
 
-const file_hint_t file_hint_hm= {
-  .extension="hm",
-  .description="HyperMesh, structural analysis software",
-  .max_filesize=PHOTOREC_MAX_FILE_SIZE,
-  .recover=1,
-  .enable_by_default=1,
-  .register_header_check=&register_header_check_hm
+const file_hint_t file_hint_hm = {
+  .extension = "hm",
+  .description = "HyperMesh, structural analysis software",
+  .max_filesize = PHOTOREC_MAX_FILE_SIZE,
+  .recover = 1,
+  .enable_by_default = 1,
+  .register_header_check = &register_header_check_hm
 };
 
+/*@
+  @ 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_hm, 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_hm(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_hm.extension;
+  file_recovery_new->extension = file_hint_hm.extension;
   return 1;
 }
 
 static void register_header_check_hm(file_stat_t *file_stat)
 {
-  static const unsigned char hm_header[23]=  {
+  static const unsigned char hm_header[23] = {
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x14, 0x40, 0x1f, 0x8b, 0x08, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x0b, 0xed