diff --git a/client.c b/client.c
index f5d3b75..625dc74 100644
--- a/client.c
+++ b/client.c
@@ -1,4 +1,5 @@
 #include <fcntl.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -9,7 +10,7 @@
 
 int main()
 {
-    long long sz;
+    ssize_t sz;
 
     char buf[1];
     char write_buf[] = "testing writing";
@@ -23,7 +24,7 @@ int main()
 
     for (int i = 0; i <= offset; i++) {
         sz = write(fd, write_buf, strlen(write_buf));
-        printf("Writing to " FIB_DEV ", returned the sequence %lld\n", sz);
+        printf("Writing to " FIB_DEV ", returned the sequence %zd\n", sz);
     }
 
     for (int i = 0; i <= offset; i++) {
@@ -31,7 +32,7 @@ int main()
         sz = read(fd, buf, 1);
         printf("Reading from " FIB_DEV
                " at offset %d, returned the sequence "
-               "%lld.\n",
+               "%zd.\n",
                i, sz);
     }
 
@@ -40,7 +41,7 @@ int main()
         sz = read(fd, buf, 1);
         printf("Reading from " FIB_DEV
                " at offset %d, returned the sequence "
-               "%lld.\n",
+               "%zd.\n",
                i, sz);
     }
 
diff --git a/fibdrv.c b/fibdrv.c
index e6af9d9..d1c7a42 100644
--- a/fibdrv.c
+++ b/fibdrv.c
@@ -33,9 +33,9 @@ static int major = 0, minor = 0;
  * Return: The k-th Fibonacci number on success, -ENOMEM on memory allocation
  * failure.
  */
-static long long fib_sequence(long long k)
+static uint64_t fib_sequence(uint64_t k)
 {
-    long long *f = kmalloc(sizeof(*f) * (k + 2), GFP_KERNEL);
+    uint64_t *f = kmalloc(sizeof(*f) * (k + 2), GFP_KERNEL);
     if (!f)
         return -ENOMEM;
 
@@ -46,7 +46,7 @@ static long long fib_sequence(long long k)
         f[i] = f[i - 1] + f[i - 2];
     }
 
-    long long ret = f[k];
+    uint64_t ret = f[k];
 
     kfree(f);