diff --git a/src/file_icns.c b/src/file_icns.c
index 22163694..ddc4dbe9 100644
--- a/src/file_icns.c
+++ b/src/file_icns.c
@@ -32,6 +32,7 @@
 #include "filegen.h"
 #include "common.h"
 
+/*@ requires \valid(file_stat); */
 static void register_header_check_icns(file_stat_t *file_stat);
 
 const file_hint_t file_hint_icns= {
@@ -56,6 +57,10 @@ struct icon_data
 //  uint8_t  data[0];
 };
 
+/*@
+  @ requires \valid_read(type + (0 .. 3));
+  @ assigns  \nothing;
+  @*/
 static int check_icon_type(const char *type)
 {
   /* https://en.wikipedia.org/wiki/Apple_Icon_Image_format */
@@ -97,6 +102,17 @@ static int check_icon_type(const char *type)
   return 0;
 }
 
+/*@
+  @ requires buffer_size >= sizeof(struct icns_header) + sizeof(struct icon_data);
+  @ 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_icns, 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_icns(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 icns_header *hdr=(const struct icns_header *)buffer;