diff --git a/src/ecmult_impl.h b/src/ecmult_impl.h
index 258615b..f6f0c42 100644
--- a/src/ecmult_impl.h
+++ b/src/ecmult_impl.h
@@ -50,8 +50,8 @@ static void secp256k1_ecmult_table_precomp_ge_storage_var(secp256k1_ge_storage_t
     secp256k1_gej_t d;
     int i;
     const int table_size = 1 << (w-2);
-    secp256k1_gej_t *prej = checked_malloc(sizeof(secp256k1_gej_t) * table_size);
-    secp256k1_ge_t *prea = checked_malloc(sizeof(secp256k1_ge_t) * table_size);
+    secp256k1_gej_t *prej = (secp256k1_gej_t *)checked_malloc(sizeof(secp256k1_gej_t) * table_size);
+    secp256k1_ge_t *prea = (secp256k1_ge_t *)checked_malloc(sizeof(secp256k1_ge_t) * table_size);
     prej[0] = *a;
     secp256k1_gej_double_var(&d, a);
     for (i = 1; i < table_size; i++) {
diff --git a/src/group_impl.h b/src/group_impl.h
index dd408e6..0d1c7b0 100644
--- a/src/group_impl.h
+++ b/src/group_impl.h
@@ -77,14 +77,14 @@ static void secp256k1_ge_set_all_gej_var(size_t len, secp256k1_ge_t *r, const se
     secp256k1_fe_t *azi;
     size_t i;
     size_t count = 0;
-    az = checked_malloc(sizeof(secp256k1_fe_t) * len);
+    az = (secp256k1_fe_t *)checked_malloc(sizeof(secp256k1_fe_t) * len);
     for (i = 0; i < len; i++) {
         if (!a[i].infinity) {
             az[count++] = a[i].z;
         }
     }
 
-    azi = checked_malloc(sizeof(secp256k1_fe_t) * count);
+    azi = (secp256k1_fe_t *)checked_malloc(sizeof(secp256k1_fe_t) * count);
     secp256k1_fe_inv_all_var(count, azi, az);
     free(az);
 
diff --git a/src/secp256k1.c b/src/secp256k1.c
index 8c4eca4..c132017 100644
--- a/src/secp256k1.c
+++ b/src/secp256k1.c
@@ -66,7 +66,7 @@ int secp256k1_ecdsa_verify(const unsigned char *msg32, const unsigned char *sig,
 static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, unsigned int counter, const void *data) {
    secp256k1_rfc6979_hmac_sha256_t rng;
    unsigned int i;
-   secp256k1_rfc6979_hmac_sha256_initialize(&rng, key32, 32, msg32, 32, data, data != NULL ? 32 : 0);
+   secp256k1_rfc6979_hmac_sha256_initialize(&rng, key32, 32, msg32, 32, (const unsigned char*)data, data != NULL ? 32 : 0);
    for (i = 0; i <= counter; i++) {
        secp256k1_rfc6979_hmac_sha256_generate(&rng, nonce32, 32);
    }
diff --git a/src/tests.c b/src/tests.c
index 91d3dae..6c473a0 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -884,8 +884,8 @@ void test_ge(void) {
      * All magnitudes are randomized.
      * All 17*17 combinations of points are added to eachother, using all applicable methods.
      */
-    secp256k1_ge_t *ge = malloc(sizeof(secp256k1_ge_t) * (1 + 4 * runs));
-    secp256k1_gej_t *gej = malloc(sizeof(secp256k1_gej_t) * (1 + 4 * runs));
+    secp256k1_ge_t *ge = (secp256k1_ge_t *)malloc(sizeof(secp256k1_ge_t) * (1 + 4 * runs));
+    secp256k1_gej_t *gej = (secp256k1_gej_t *)malloc(sizeof(secp256k1_gej_t) * (1 + 4 * runs));
     secp256k1_gej_set_infinity(&gej[0]);
     secp256k1_ge_clear(&ge[0]);
     secp256k1_ge_set_gej_var(&ge[0], &gej[0]);
@@ -961,7 +961,7 @@ void test_ge(void) {
     /* Test adding all points together in random order equals infinity. */
     {
         secp256k1_gej_t sum = SECP256K1_GEJ_CONST_INFINITY;
-        secp256k1_gej_t *gej_shuffled = malloc((4 * runs + 1) * sizeof(secp256k1_gej_t));
+        secp256k1_gej_t *gej_shuffled = (secp256k1_gej_t *)malloc((4 * runs + 1) * sizeof(secp256k1_gej_t));
         for (i = 0; i < 4 * runs + 1; i++) {
             gej_shuffled[i] = gej[i];
         }
@@ -982,7 +982,7 @@ void test_ge(void) {
 
     /* Test batch gej -> ge conversion. */
     {
-        secp256k1_ge_t *ge_set_all = malloc((4 * runs + 1) * sizeof(secp256k1_ge_t));
+        secp256k1_ge_t *ge_set_all = (secp256k1_ge_t *)malloc((4 * runs + 1) * sizeof(secp256k1_ge_t));
         secp256k1_ge_set_all_gej_var(4 * runs + 1, ge_set_all, gej);
         for (i = 0; i < 4 * runs + 1; i++) {
             ge_equals_gej(&ge_set_all[i], &gej[i]);