diff --git a/src/cac-aca.c b/src/cac-aca.c

index 9e305a8..e66b089 100644

--- a/src/cac-aca.c

+++ b/src/cac-aca.c

@@ -60,7 +60,7 @@ struct acr_entry {

     struct acr_access_method access_methods[MAX_ACCESS_METHODS];

 };

 struct acr_table {

-    unsigned int num_entries;

+    unsigned char num_entries;

     struct acr_entry entries[];

 };

diff --git a/tests/libcacard.c b/tests/libcacard.c

index 0c6cca1..18ccf6f 100644

--- a/tests/libcacard.c

+++ b/tests/libcacard.c

@@ -179,7 +179,7 @@ static void parse_acr(uint8_t *buf, int buflen)

 {

     uint8_t *p, *p_end;

     int have_applet_information = 0;

-    int num_entries = 0, num_entries_expected = -1;

+    uint8_t num_entries = 0, num_entries_expected = 255;

     p = buf;

     p_end = p + buflen - 2;

@@ -204,7 +204,7 @@ static void parse_acr(uint8_t *buf, int buflen)

         case 0x81: /* Num Applet/Objects */

         case 0x91: /* Num AMP Entries */

         case 0x94: /* Num Service Applet Entries */

-            g_assert_cmpint(num_entries_expected, ==, -1);

+            g_assert_cmpint(num_entries_expected, ==, 255);

             g_assert_cmpint(num_entries, ==, 0);

             num_entries_expected = *p;

             break;

@@ -230,7 +230,7 @@ static void parse_acr(uint8_t *buf, int buflen)

     /* Every response needs to have exactly one applet information tag */

     g_assert_cmpint(have_applet_information, ==, 1);

     /* The number of entries in the second tag matches the number of entries later */

-    if (num_entries_expected != -1) {

+    if (num_entries_expected != 255) {

         g_assert_cmpint(num_entries, ==, num_entries_expected);

     }

     /* nothing left to read */