diff --git a/src/ecmult_gen_impl.h b/src/ecmult_gen_impl.h
index 7079c31418..36a6fd9e82 100644
--- a/src/ecmult_gen_impl.h
+++ b/src/ecmult_gen_impl.h
@@ -80,7 +80,7 @@ static void secp256k1_ecmult_gen_start(void) {
     for (int j=0; j<64; j++) {
         for (int i=0; i<16; i++) {
             const unsigned char* raw = (const unsigned char*)(&prec[j*16 + i]);
-            for (int k=0; k<sizeof(secp256k1_ge_t); k++)
+            for (size_t k=0; k<sizeof(secp256k1_ge_t); k++)
                 ret->prec[j][k][i] = raw[k];
         }
     }
@@ -105,7 +105,7 @@ static void secp256k1_ecmult_gen(secp256k1_gej_t *r, const secp256k1_scalar_t *g
     int bits;
     for (int j=0; j<64; j++) {
         bits = secp256k1_scalar_get_bits(gn, j * 4, 4);
-        for (int k=0; k<sizeof(secp256k1_ge_t); k++)
+        for (size_t k=0; k<sizeof(secp256k1_ge_t); k++)
             ((unsigned char*)(&add))[k] = c->prec[j][k][bits];
         secp256k1_gej_add_ge(r, r, &add);
     }
diff --git a/src/field_impl.h b/src/field_impl.h
index 3223d53848..1e52343c8c 100644
--- a/src/field_impl.h
+++ b/src/field_impl.h
@@ -222,7 +222,7 @@ static void secp256k1_fe_inv_all(size_t len, secp256k1_fe_t r[len], const secp25
 
     r[0] = a[0];
 
-    int i = 0;
+    size_t i = 0;
     while (++i < len) {
         secp256k1_fe_mul(&r[i], &r[i - 1], &a[i]);
     }
@@ -246,7 +246,7 @@ static void secp256k1_fe_inv_all_var(size_t len, secp256k1_fe_t r[len], const se
 
     r[0] = a[0];
 
-    int i = 0;
+    size_t i = 0;
     while (++i < len) {
         secp256k1_fe_mul(&r[i], &r[i - 1], &a[i]);
     }
diff --git a/src/group_impl.h b/src/group_impl.h
index 9d10a64aad..7becd2c0e5 100644
--- a/src/group_impl.h
+++ b/src/group_impl.h
@@ -82,9 +82,9 @@ static void secp256k1_ge_set_gej_var(secp256k1_ge_t *r, secp256k1_gej_t *a) {
 }
 
 static void secp256k1_ge_set_all_gej_var(size_t len, secp256k1_ge_t r[len], const secp256k1_gej_t a[len]) {
-    int count = 0;
+    size_t count = 0;
     secp256k1_fe_t az[len];
-    for (int i=0; i<len; i++) {
+    for (size_t i=0; i<len; i++) {
         if (!a[i].infinity) {
             az[count++] = a[i].z;
         }
@@ -94,7 +94,7 @@ static void secp256k1_ge_set_all_gej_var(size_t len, secp256k1_ge_t r[len], cons
     secp256k1_fe_inv_all_var(count, azi, az);
 
     count = 0;
-    for (int i=0; i<len; i++) {
+    for (size_t i=0; i<len; i++) {
         r[i].infinity = a[i].infinity;
         if (!a[i].infinity) {
             secp256k1_fe_t *zi = &azi[count++];
diff --git a/src/num_gmp_impl.h b/src/num_gmp_impl.h
index b6eac97e28..36a24646b0 100644
--- a/src/num_gmp_impl.h
+++ b/src/num_gmp_impl.h
@@ -57,7 +57,7 @@ static void secp256k1_num_get_bin(unsigned char *r, unsigned int rlen, const sec
     }
     int shift = 0;
     while (shift < len && tmp[shift] == 0) shift++;
-    VERIFY_CHECK(len-shift <= rlen);
+    VERIFY_CHECK(len-shift <= (int)rlen);
     memset(r, 0, rlen - len + shift);
     if (len > shift) {
         memcpy(r + rlen - len + shift, tmp + shift, len - shift);