diff --git a/tests/simpletlv.c b/tests/simpletlv.c
index cd0cd69c4dfb504a52e3f7314e4a01657377eb68..9ddc5b999f73d56f35f85810479760b301330282 100644
--- a/tests/simpletlv.c
+++ b/tests/simpletlv.c
@@ -48,7 +48,7 @@ static void test_length_simple(void)
 
 static void test_length_nested(void)
 {
-    size_t length = 0;
+    int length = 0;
     unsigned char simple_value[] = "\x12\x14";
     static struct simpletlv_member simple[1] = {
       {0x25, 2, {/*.value = simple_value*/}, SIMPLETLV_TYPE_LEAF}
@@ -102,7 +102,7 @@ static void test_length_skipped(void)
 static void test_encode_simple(void)
 {
     unsigned char *result = NULL;
-    size_t result_len = 0;
+    int result_len = 0;
     unsigned char simple_value[] = "\x10\x11";
     unsigned char simple_encoded[] = "\x25\x02\x10\x11";
     unsigned char long_value[256] = "Long data value";
@@ -168,7 +168,7 @@ static void test_encode_simple(void)
 static void test_encode_nested(void)
 {
     unsigned char *result = NULL;
-    size_t result_len = 0;
+    int result_len = 0;
     unsigned char simple_value[] = "\x12\x14";
     unsigned char encoded[] = "\x72\x04\x25\x02\x12\x14";
     static struct simpletlv_member simple[1] = {