diff --git a/sha-256.c b/sha-256.c
index ba758bd..db044aa 100644
--- a/sha-256.c
+++ b/sha-256.c
@@ -93,30 +93,31 @@ static int calc_chunk(uint8_t chunk[CHUNK_SIZE], struct buffer_state * state)
 		memset(chunk, 0x00, left);
 		chunk += left;
 
-		if (sizeof len > 4) {
-			chunk[0] = (uint8_t) (len >> 56);
-			chunk[1] = (uint8_t) (len >> 48);
-			chunk[2] = (uint8_t) (len >> 40);
-			chunk[3] = (uint8_t) (len >> 32);
-		} else {
-			chunk[0] = 0;
-			chunk[1] = 0;
-			chunk[2] = 0;
-			chunk[3] = 0;
-		}
-		if (sizeof len > 2) {
-			chunk[4] = (uint8_t) (len >> 24);
-			chunk[5] = (uint8_t) (len >> 16);
-		} else {
-			chunk[4] = 0;
-			chunk[5] = 0;
-		}
+#if SIZE_MAX > UINT32_MAX
+		chunk[0] = (uint8_t) (len >> 56);
+		chunk[1] = (uint8_t) (len >> 48);
+		chunk[2] = (uint8_t) (len >> 40);
+		chunk[3] = (uint8_t) (len >> 32);
+#else
+		chunk[0] = 0;
+		chunk[1] = 0;
+		chunk[2] = 0;
+		chunk[3] = 0;
+#endif
+
+#if SIZE_MAX > UINT16_MAX
+		chunk[4] = (uint8_t) (len >> 24);
+		chunk[5] = (uint8_t) (len >> 16);
+#else
+		chunk[4] = 0;
+		chunk[5] = 0;
+#endif
 		
-		if (sizeof len > 1) {
-			chunk[6] = (uint8_t) (len >> 8);
-		} else {
-			chunk[6] = 0;
-		}
+#if SIZE_MAX > UINT8_MAX
+		chunk[6] = (uint8_t) (len >> 8);
+#else
+		chunk[6] = 0;
+#endif
 		
 		chunk[7] = (uint8_t) len;
 
@@ -181,16 +182,17 @@ void calc_sha_256(uint8_t hash[32], const void * input, size_t len)
 		 */
 		uint32_t w[64];
 		const uint8_t *p = chunk;
+		int i;
 
 		memset(w, 0x00, sizeof w);
-		for (int i = 0; i < 16; i++) {
+		for (i = 0; i < 16; i++) {
 			w[i] = (uint32_t) p[0] << 24 | (uint32_t) p[1] << 16 |
 				(uint32_t) p[2] << 8 | (uint32_t) p[3];
 			p += 4;
 		}
 
 		/* Extend the first 16 words into the remaining 48 words w[16..63] of the message schedule array: */
-		for (int i = 16; i < 64; i++) {
+		for (i = 16; i < 64; i++) {
 			const uint32_t s0 = right_rot(w[i - 15], 7) ^ right_rot(w[i - 15], 18) ^ (w[i - 15] >> 3);
 			const uint32_t s1 = right_rot(w[i - 2], 17) ^ right_rot(w[i - 2], 19) ^ (w[i - 2] >> 10);
 			w[i] = w[i - 16] + s0 + w[i - 7] + s1;
@@ -207,7 +209,7 @@ void calc_sha_256(uint8_t hash[32], const void * input, size_t len)
 		h = h7;
 
 		/* Compression function main loop: */
-		for (int i = 0; i < 64; i++) {
+		for (i = 0; i < 64; i++) {
 			const uint32_t s1 = right_rot(e, 6) ^ right_rot(e, 11) ^ right_rot(e, 25);
 			const uint32_t ch = (e & f) ^ (~e & g);
 			const uint32_t temp1 = h + s1 + ch + k[i] + w[i];
diff --git a/test.c b/test.c
index 19edd9a..9098af2 100644
--- a/test.c
+++ b/test.c
@@ -35,15 +35,40 @@ static const struct vector VECTORS[] = {
 		"248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1"
 	},
 	{
-		"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmnoi"
-		"jklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu",
+		"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmno"
+		"ijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu",
 		"cf5b16a778af8380036ce59e7b0492370b249b11e8f07a51afac45037afee9d1"
+	},
+	{
+		"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmno"
+		"ijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghi"
+		"cdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopq"
+		"klmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijk"
+		"efghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrs"
+		"mnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijkefghijklfghijklm"
+		"ghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+		"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmno"
+		"ijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghi"
+		"cdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopq"
+		"klmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijk"
+		"efghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrs"
+		"mnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijkefghijklfghijklm"
+		"ghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu"
+		"abcdefghbcdefghicdefghijdefghijkefghijklfghijklmghijklmnhijklmno"
+		"ijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghi"
+		"cdefghijdefghijkefghijklfghijklmghijklmnhijklmnoijklmnopjklmnopq"
+		"klmnopqrlmnopqrsmnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijk"
+		"efghijklfghijklmghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrs"
+		"mnopqrstnopqrstuabcdefghbcdefghicdefghijdefghijkefghijklfghijklm"
+		"ghijklmnhijklmnoijklmnopjklmnopqklmnopqrlmnopqrsmnopqrstnopqrstu",
+		"c7273f978615fc09e6a567bb28586fa30b76a2c915ffcdc728d3414fceb63493"
 	}
 };
 
 static void hash_to_string(char string[65], const uint8_t hash[32])
 {
-	for (size_t i = 0; i < 32; i++) {
+	size_t i;
+	for (i = 0; i < 32; i++) {
 		string += sprintf(string, "%02x", hash[i]);
 	}
 }	
@@ -66,7 +91,8 @@ static void test(const char input[], const char output[])
 
 int main(void)
 {
-	for (size_t i = 0; i < (sizeof VECTORS / sizeof (struct vector)); i++) {
+	size_t i;
+	for (i = 0; i < (sizeof VECTORS / sizeof (struct vector)); i++) {
 		const struct vector *vector = &VECTORS[i];
 		test(vector->input, vector->output);
 	}