diff --git a/3_RootkitTechniques/3.7_char_interfering/rootkit.c b/3_RootkitTechniques/3.7_char_interfering/rootkit.c
index e8f2e0b..dc377f0 100644
--- a/3_RootkitTechniques/3.7_char_interfering/rootkit.c
+++ b/3_RootkitTechniques/3.7_char_interfering/rootkit.c
@@ -34,7 +34,7 @@
 
     if(error)
     {
-        printk(KERN_DEBUG "rootkit: %d bytes could not be copied into kbuf\n", error);
+        printk(KERN_DEBUG "rootkit: %ld bytes could not be copied into kbuf\n", error);
         kfree(kbuf);
         return bytes_read;
     }
@@ -48,7 +48,7 @@
      */
     error = copy_to_user(buf, kbuf, bytes_read);
     if (error)
-        printk(KERN_DEBUG "rootkit: %d bytes could not be copied into buf\n", error);
+        printk(KERN_DEBUG "rootkit: %ld bytes could not be copied into buf\n", error);
 
     kfree(kbuf);
     return bytes_read;
@@ -72,7 +72,7 @@
 
     if(error)
     {
-        printk(KERN_DEBUG "rootkit: %d bytes could not be copied into kbuf\n", error);
+        printk(KERN_DEBUG "rootkit: %ld bytes could not be copied into kbuf\n", error);
         kfree(kbuf);
         return bytes_read;
     }
@@ -86,7 +86,7 @@
      */
     error = copy_to_user(buf, kbuf, bytes_read);
     if (error)
-        printk(KERN_DEBUG "rootkit: %d bytes could not be copied into buf\n", error);
+        printk(KERN_DEBUG "rootkit: %ld bytes could not be copied into buf\n", error);
 
     kfree(kbuf);
     return bytes_read;