diff --git a/crypto_kem/frodokem640shake/clean/common.h b/crypto_kem/frodokem640shake/clean/common.h
index c3671abc..aa19ea07 100644
--- a/crypto_kem/frodokem640shake/clean/common.h
+++ b/crypto_kem/frodokem640shake/clean/common.h
@@ -10,8 +10,8 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_add(uint16_t *out, const uint16_t *a, const
 void PQCLEAN_FRODOKEM640SHAKE_CLEAN_sub(uint16_t *out, const uint16_t *a, const uint16_t *b);
 void PQCLEAN_FRODOKEM640SHAKE_CLEAN_key_encode(uint16_t *out, const uint16_t *in);
 void PQCLEAN_FRODOKEM640SHAKE_CLEAN_key_decode(uint16_t *out, const uint16_t *in);
-void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(unsigned char *out, size_t outlen, const uint16_t *in, size_t inlen, unsigned char lsb);
-void PQCLEAN_FRODOKEM640SHAKE_CLEAN_unpack(uint16_t *out, size_t outlen, const unsigned char *in, size_t inlen, unsigned char lsb);
+void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(uint8_t *out, size_t outlen, const uint16_t *in, size_t inlen, uint8_t lsb);
+void PQCLEAN_FRODOKEM640SHAKE_CLEAN_unpack(uint16_t *out, size_t outlen, const uint8_t *in, size_t inlen, uint8_t lsb);
 void PQCLEAN_FRODOKEM640SHAKE_CLEAN_clear_bytes(uint8_t *mem, size_t n);
 uint16_t PQCLEAN_FRODOKEM640SHAKE_CLEAN_LE_TO_UINT16(uint16_t n);
 uint16_t PQCLEAN_FRODOKEM640SHAKE_CLEAN_UINT16_TO_LE(uint16_t n);
diff --git a/crypto_kem/frodokem640shake/clean/kem.c b/crypto_kem/frodokem640shake/clean/kem.c
index 8dd0ba2e..ff2b9f46 100644
--- a/crypto_kem/frodokem640shake/clean/kem.c
+++ b/crypto_kem/frodokem640shake/clean/kem.c
@@ -14,7 +14,7 @@
 #include "common.h"
 #include "params.h"
 
-int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_keypair(unsigned char *pk, unsigned char *sk) {
+int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_keypair(uint8_t *pk, uint8_t *sk) {
     // FrodoKEM's key generation
     // Outputs: public key pk (               BYTES_SEED_A + (PARAMS_LOGQ*PARAMS_N*PARAMS_NBAR)/8 bytes)
     //          secret key sk (CRYPTO_BYTES + BYTES_SEED_A + (PARAMS_LOGQ*PARAMS_N*PARAMS_NBAR)/8 + 2*PARAMS_N*PARAMS_NBAR + BYTES_PKHASH bytes)
@@ -71,7 +71,7 @@ int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_keypair(unsigned char *pk, unsigne
 }
 
 
-int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_enc(unsigned char *ct, unsigned char *ss, const unsigned char *pk) {
+int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_enc(uint8_t *ct, uint8_t *ss, const uint8_t *pk) {
     // FrodoKEM's key encapsulation
     const uint8_t *pk_seedA = &pk[0];
     const uint8_t *pk_b = &pk[BYTES_SEED_A];
@@ -140,7 +140,7 @@ int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_enc(unsigned char *ct, unsigned ch
 }
 
 
-int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_dec(unsigned char *ss, const unsigned char *ct, const unsigned char *sk) {
+int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_dec(uint8_t *ss, const uint8_t *ct, const uint8_t *sk) {
     // FrodoKEM's key decapsulation
     uint16_t B[PARAMS_N * PARAMS_NBAR] = {0};
     uint16_t Bp[PARAMS_N * PARAMS_NBAR] = {0};
@@ -210,7 +210,7 @@ int PQCLEAN_FRODOKEM640SHAKE_CLEAN_crypto_kem_dec(unsigned char *ss, const unsig
     memcpy(Fin_ct, ct, CRYPTO_CIPHERTEXTBYTES);
 
     // Reducing BBp modulo q
-    for (int i = 0; i < PARAMS_N * PARAMS_NBAR; i++) {
+    for (size_t i = 0; i < PARAMS_N * PARAMS_NBAR; i++) {
         BBp[i] = BBp[i] & ((1 << PARAMS_LOGQ) - 1);
     }
 
diff --git a/crypto_kem/frodokem640shake/clean/matrix_shake.c b/crypto_kem/frodokem640shake/clean/matrix_shake.c
index 78c67174..5524b975 100644
--- a/crypto_kem/frodokem640shake/clean/matrix_shake.c
+++ b/crypto_kem/frodokem640shake/clean/matrix_shake.c
@@ -25,7 +25,7 @@ int PQCLEAN_FRODOKEM640SHAKE_CLEAN_mul_add_as_plus_e(uint16_t *out, const uint16
     memcpy(&seed_A_separated[2], seed_A, BYTES_SEED_A);
     for (i = 0; i < PARAMS_N; i++) {
         seed_A_origin[0] = PQCLEAN_FRODOKEM640SHAKE_CLEAN_UINT16_TO_LE((uint16_t) i);
-        shake128((unsigned char *)(A + i * PARAMS_N), (unsigned long long)(2 * PARAMS_N), seed_A_separated, 2 + BYTES_SEED_A);
+        shake128((uint8_t *)(A + i * PARAMS_N), (unsigned long long)(2 * PARAMS_N), seed_A_separated, 2 + BYTES_SEED_A);
     }
     for (i = 0; i < PARAMS_N * PARAMS_N; i++) {
         A[i] = PQCLEAN_FRODOKEM640SHAKE_CLEAN_LE_TO_UINT16(A[i]);
@@ -58,7 +58,7 @@ int PQCLEAN_FRODOKEM640SHAKE_CLEAN_mul_add_sa_plus_e(uint16_t *out, const uint16
     memcpy(&seed_A_separated[2], seed_A, BYTES_SEED_A);
     for (i = 0; i < PARAMS_N; i++) {
         seed_A_origin[0] = PQCLEAN_FRODOKEM640SHAKE_CLEAN_UINT16_TO_LE((uint16_t) i);
-        shake128((unsigned char *)(A + i * PARAMS_N), (unsigned long long)(2 * PARAMS_N), seed_A_separated, 2 + BYTES_SEED_A);
+        shake128((uint8_t *)(A + i * PARAMS_N), (unsigned long long)(2 * PARAMS_N), seed_A_separated, 2 + BYTES_SEED_A);
     }
     for (i = 0; i < PARAMS_N * PARAMS_N; i++) {
         A[i] = PQCLEAN_FRODOKEM640SHAKE_CLEAN_LE_TO_UINT16(A[i]);
diff --git a/crypto_kem/frodokem640shake/clean/util.c b/crypto_kem/frodokem640shake/clean/util.c
index 26d49a62..ba038d1d 100644
--- a/crypto_kem/frodokem640shake/clean/util.c
+++ b/crypto_kem/frodokem640shake/clean/util.c
@@ -65,7 +65,7 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_add(uint16_t *out, const uint16_t *a, const
     // Inputs: a, b (N_BAR x N_BAR)
     // Output: c = a + b
 
-    for (int i = 0; i < (PARAMS_NBAR * PARAMS_NBAR); i++) {
+    for (size_t i = 0; i < (PARAMS_NBAR * PARAMS_NBAR); i++) {
         out[i] = (a[i] + b[i]) & ((1 << PARAMS_LOGQ) - 1);
     }
 }
@@ -76,7 +76,7 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_sub(uint16_t *out, const uint16_t *a, const
     // Inputs: a, b (N_BAR x N_BAR)
     // Output: c = a - b
 
-    for (int i = 0; i < (PARAMS_NBAR * PARAMS_NBAR); i++) {
+    for (size_t i = 0; i < (PARAMS_NBAR * PARAMS_NBAR); i++) {
         out[i] = (a[i] - b[i]) & ((1 << PARAMS_LOGQ) - 1);
     }
 }
@@ -125,7 +125,7 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_key_decode(uint16_t *out, const uint16_t *in
 }
 
 
-void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(unsigned char *out, const size_t outlen, const uint16_t *in, const size_t inlen, const unsigned char lsb) {
+void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(uint8_t *out, const size_t outlen, const uint16_t *in, const size_t inlen, const uint8_t lsb) {
     // Pack the input uint16 vector into a char output vector, copying lsb bits from each input element.
     // If inlen * lsb / 8 > outlen, only outlen * 8 bits are copied.
     memset(out, 0, outlen);
@@ -133,7 +133,7 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(unsigned char *out, const size_t outlen
     size_t i = 0;            // whole bytes already filled in
     size_t j = 0;            // whole uint16_t already copied
     uint16_t w = 0;          // the leftover, not yet copied
-    unsigned char bits = 0;  // the number of lsb in w
+    uint8_t bits = 0;        // the number of lsb in w
 
     while (i < outlen && (j < inlen || ((j == inlen) && (bits > 0)))) {
         /*
@@ -147,14 +147,14 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(unsigned char *out, const size_t outlen
                                     ^^
                                     ib
         */
-        unsigned char b = 0;  // bits in out[i] already filled in
+        uint8_t b = 0;  // bits in out[i] already filled in
         while (b < 8) {
             int nbits = min(8 - b, bits);
             uint16_t mask = (1 << nbits) - 1;
-            unsigned char t = (unsigned char) ((w >> (bits - nbits)) & mask);  // the bits to copy from w to out
+            uint8_t t = (uint8_t) ((w >> (bits - nbits)) & mask);  // the bits to copy from w to out
             out[i] = out[i] + (t << (8 - b - nbits));
-            b += (unsigned char) nbits;
-            bits -= (unsigned char) nbits;
+            b += (uint8_t) nbits;
+            bits -= (uint8_t) nbits;
             w &= ~(mask << bits);  // not strictly necessary; mostly for debugging
 
             if (bits == 0) {
@@ -174,15 +174,15 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_pack(unsigned char *out, const size_t outlen
 }
 
 
-void PQCLEAN_FRODOKEM640SHAKE_CLEAN_unpack(uint16_t *out, const size_t outlen, const unsigned char *in, const size_t inlen, const unsigned char lsb) {
+void PQCLEAN_FRODOKEM640SHAKE_CLEAN_unpack(uint16_t *out, const size_t outlen, const uint8_t *in, const size_t inlen, const uint8_t lsb) {
     // Unpack the input char vector into a uint16_t output vector, copying lsb bits
     // for each output element from input. outlen must be at least ceil(inlen * 8 / lsb).
     memset(out, 0, outlen * sizeof(uint16_t));
 
     size_t i = 0;            // whole uint16_t already filled in
     size_t j = 0;            // whole bytes already copied
-    unsigned char w = 0;     // the leftover, not yet copied
-    unsigned char bits = 0;  // the number of lsb bits of w
+    uint8_t w = 0;           // the leftover, not yet copied
+    uint8_t bits = 0;        // the number of lsb bits of w
 
     while (i < outlen && (j < inlen || ((j == inlen) && (bits > 0)))) {
         /*
@@ -196,14 +196,14 @@ void PQCLEAN_FRODOKEM640SHAKE_CLEAN_unpack(uint16_t *out, const size_t outlen, c
                               ^   ^
                               i   b
         */
-        unsigned char b = 0;  // bits in out[i] already filled in
+        uint8_t b = 0;  // bits in out[i] already filled in
         while (b < lsb) {
             int nbits = min(lsb - b, bits);
             uint16_t mask = (1 << nbits) - 1;
-            unsigned char t = (w >> (bits - nbits)) & mask;  // the bits to copy from w to out
+            uint8_t t = (w >> (bits - nbits)) & mask;  // the bits to copy from w to out
             out[i] = out[i] + (t << (lsb - b - nbits));
-            b += (unsigned char) nbits;
-            bits -= (unsigned char) nbits;
+            b += (uint8_t) nbits;
+            bits -= (uint8_t) nbits;
             w &= ~(mask << bits);  // not strictly necessary; mostly for debugging
 
             if (bits == 0) {
diff --git a/test/crypto_kem/functest.c b/test/crypto_kem/functest.c
index 74cef3f6..7f50608b 100644
--- a/test/crypto_kem/functest.c
+++ b/test/crypto_kem/functest.c
@@ -15,13 +15,13 @@ const uint8_t canary[8] = {
  * make sure it is not touched by the implementations.
  */
 static void write_canary(uint8_t *d) {
-    for (int i = 0; i < 8; i++) {
+    for (size_t i = 0; i < 8; i++) {
         d[i] = canary[i];
     }
 }
 
 static int check_canary(const uint8_t *d) {
-    for (int i = 0; i < 8; i++) {
+    for (size_t i = 0; i < 8; i++) {
         if (d[i] != canary[i]) {
             return -1;
         }
diff --git a/test/crypto_sign/functest.c b/test/crypto_sign/functest.c
index 57e9e0da..9fb3a1b9 100644
--- a/test/crypto_sign/functest.c
+++ b/test/crypto_sign/functest.c
@@ -17,13 +17,13 @@ const uint8_t canary[8] = {
  * make sure it is not touched by the implementations.
  */
 static void write_canary(uint8_t *d) {
-    for (int i = 0; i < 8; i++) {
+    for (size_t i = 0; i < 8; i++) {
         d[i] = canary[i];
     }
 }
 
 static int check_canary(const uint8_t *d) {
-    for (int i = 0; i < 8; i++) {
+    for (size_t i = 0; i < 8; i++) {
         if (d[i] != canary[i]) {
             return -1;
         }