diff --git a/test/unit/core/test_pbuf.c b/test/unit/core/test_pbuf.c
index bda583a7..36aff132 100644
--- a/test/unit/core/test_pbuf.c
+++ b/test/unit/core/test_pbuf.c
@@ -164,8 +164,8 @@ START_TEST(test_pbuf_take_at_edge)
   res = pbuf_take_at(p, &testdata, sizeof(testdata), 0);
   fail_unless(res == ERR_OK);
 
-  out = p->payload;
-  for (i = 0; i < sizeof(testdata); i++) {
+  out = (u8_t*)p->payload;
+  for (i = 0; i < (int)sizeof(testdata); i++) {
     fail_unless(out[i] == testdata[i],
       "Bad data at pos %d, was %02X, expected %02X", i, out[i], testdata[i]);
   }
@@ -174,11 +174,11 @@ START_TEST(test_pbuf_take_at_edge)
   res = pbuf_take_at(p, &testdata, sizeof(testdata), p->len - 1);
   fail_unless(res == ERR_OK);
 
-  out = p->payload;
+  out = (u8_t*)p->payload;
   fail_unless(out[p->len - 1] == testdata[0],
     "Bad data at pos %d, was %02X, expected %02X", p->len - 1, out[p->len - 1], testdata[0]);
-  out = q->payload;
-  for (i = 1; i < sizeof(testdata); i++) {
+  out = (u8_t*)q->payload;
+  for (i = 1; i < (int)sizeof(testdata); i++) {
     fail_unless(out[i-1] == testdata[i],
       "Bad data at pos %d, was %02X, expected %02X", p->len - 1 + i, out[i-1], testdata[i]);
   }
@@ -187,8 +187,8 @@ START_TEST(test_pbuf_take_at_edge)
   res = pbuf_take_at(p, &testdata, sizeof(testdata), p->len);
   fail_unless(res == ERR_OK);
 
-  out = p->payload;
-  for (i = 0; i < sizeof(testdata); i++) {
+  out = (u8_t*)p->payload;
+  for (i = 0; i < (int)sizeof(testdata); i++) {
     fail_unless(out[i] == testdata[i],
       "Bad data at pos %d, was %02X, expected %02X", p->len+i, out[i], testdata[i]);
   }
@@ -214,7 +214,7 @@ START_TEST(test_pbuf_get_put_at_edge)
   /* put byte at the beginning of second pbuf */
   pbuf_put_at(p, p->len, testdata);
 
-  out = q->payload;
+  out = (u8_t*)q->payload;
   fail_unless(*out == testdata,
     "Bad data at pos %d, was %02X, expected %02X", p->len, *out, testdata);
 
diff --git a/test/unit/dhcp/test_dhcp.c b/test/unit/dhcp/test_dhcp.c
index 2ceca097..38b0f7a5 100644
--- a/test/unit/dhcp/test_dhcp.c
+++ b/test/unit/dhcp/test_dhcp.c
@@ -203,7 +203,7 @@ static void check_pkt(struct pbuf *p, u32_t pos, const u8_t *mem, u32_t len)
   fail_if(p == NULL);
   fail_unless(pos + len <= p->len); /* All data we seek within same pbuf */
 
-  data = p->payload;
+  data = (u8_t*)p->payload;
   fail_if(memcmp(&data[pos], mem, len), "data at pos %d, len %d in packet %d did not match", pos, len, txpacket);
 }
 
@@ -222,7 +222,7 @@ static void check_pkt_fuzzy(struct pbuf *p, u32_t startpos, const u8_t *mem, u32
   fail_unless(startpos + len <= p->len); /* All data we seek within same pbuf */
 
   found = 0;
-  data = p->payload;
+  data = (u8_t*)p->payload;
   for (i = startpos; i <= (p->len - len); i++) {
     if (memcmp(&data[i], mem, len) == 0) {
       found = 1;
@@ -301,6 +301,9 @@ static err_t lwip_tx_func(struct netif *netif, struct pbuf *p)
         check_pkt(p, 12, arpproto, sizeof(arpproto)); /* eth level proto: ip */
         break;
       }
+      default:
+        fail();
+        break;
     }
     break;
 
@@ -405,6 +408,9 @@ static err_t lwip_tx_func(struct netif *netif, struct pbuf *p)
         check_pkt_fuzzy(p, 282, dhcp_request_opt, sizeof(dhcp_request_opt));
         break;
       }
+    default:
+      fail();
+      break;
     }
     break;
 
diff --git a/test/unit/etharp/test_etharp.c b/test/unit/etharp/test_etharp.c
index 1034c39e..ba9a40dc 100644
--- a/test/unit/etharp/test_etharp.c
+++ b/test/unit/etharp/test_etharp.c
@@ -160,11 +160,11 @@ START_TEST(test_etharp_table)
       struct pbuf *p = pbuf_alloc(PBUF_TRANSPORT, 10, PBUF_RAM);
       fail_unless(p != NULL);
       if (p != NULL) {
-        err_t err;
+        err_t err2;
         ip_addr_t dst;
         ip_addr_copy_from_ip4(dst, adrs[i]);
-        err = udp_sendto(pcb, p, &dst, 123);
-        fail_unless(err == ERR_OK);
+        err2 = udp_sendto(pcb, p, &dst, 123);
+        fail_unless(err2 == ERR_OK);
         /* etharp request sent? */
         fail_unless(linkoutput_ctr == (2*i) + 1);
         pbuf_free(p);
@@ -195,11 +195,11 @@ START_TEST(test_etharp_table)
       struct pbuf *p = pbuf_alloc(PBUF_TRANSPORT, 10, PBUF_RAM);
       fail_unless(p != NULL);
       if (p != NULL) {
-        err_t err;
+        err_t err2;
         ip_addr_t dst;
         ip_addr_copy_from_ip4(dst, adrs[i]);
-        err = udp_sendto(pcb, p, &dst, 123);
-        fail_unless(err == ERR_OK);
+        err2 = udp_sendto(pcb, p, &dst, 123);
+        fail_unless(err2 == ERR_OK);
         /* etharp request sent? */
         fail_unless(linkoutput_ctr == (2*i) + 1);
         pbuf_free(p);
diff --git a/test/unit/tcp/tcp_helper.c b/test/unit/tcp/tcp_helper.c
index e25956af..1a2ae06b 100644
--- a/test/unit/tcp/tcp_helper.c
+++ b/test/unit/tcp/tcp_helper.c
@@ -62,7 +62,7 @@ tcp_create_segment_wnd(ip_addr_t* src_ip, ip_addr_t* dst_ip,
     memset(q->payload, 0, q->len);
   }
 
-  iphdr = p->payload;
+  iphdr = (struct ip_hdr*)p->payload;
   /* fill IP header */
   iphdr->dest.addr = ip_2_ip4(dst_ip)->addr;
   iphdr->src.addr = ip_2_ip4(src_ip)->addr;
@@ -74,7 +74,7 @@ tcp_create_segment_wnd(ip_addr_t* src_ip, ip_addr_t* dst_ip,
   /* let p point to TCP header */
   pbuf_header(p, -(s16_t)sizeof(struct ip_hdr));
 
-  tcphdr = p->payload;
+  tcphdr = (struct tcp_hdr*)p->payload;
   tcphdr->src   = htons(src_port);
   tcphdr->dest  = htons(dst_port);
   tcphdr->seqno = htonl(seqno);
@@ -168,7 +168,7 @@ tcp_set_state(struct tcp_pcb* pcb, enum tcp_state state, ip_addr_t* local_ip,
 void
 test_tcp_counters_err(void* arg, err_t err)
 {
-  struct test_tcp_counters* counters = arg;
+  struct test_tcp_counters* counters = (struct test_tcp_counters*)arg;
   EXPECT_RET(arg != NULL);
   counters->err_calls++;
   counters->last_err = err;
@@ -186,7 +186,7 @@ test_tcp_counters_check_rxdata(struct test_tcp_counters* counters, struct pbuf*
   EXPECT_RET(counters->recved_bytes + p->tot_len <= counters->expected_data_len);
   received = counters->recved_bytes;
   for(q = p; q != NULL; q = q->next) {
-    char *data = q->payload;
+    char *data = (char*)q->payload;
     for(i = 0; i < q->len; i++) {
       EXPECT_RET(data[i] == counters->expected_data[received]);
       received++;
@@ -198,7 +198,7 @@ test_tcp_counters_check_rxdata(struct test_tcp_counters* counters, struct pbuf*
 err_t
 test_tcp_counters_recv(void* arg, struct tcp_pcb* pcb, struct pbuf* p, err_t err)
 {
-  struct test_tcp_counters* counters = arg;
+  struct test_tcp_counters* counters = (struct test_tcp_counters*)arg;
   EXPECT_RETX(arg != NULL, ERR_OK);
   EXPECT_RETX(pcb != NULL, ERR_OK);
   EXPECT_RETX(err == ERR_OK, ERR_OK);
diff --git a/test/unit/tcp/test_tcp_oos.c b/test/unit/tcp/test_tcp_oos.c
index c2914233..354b51d5 100644
--- a/test/unit/tcp/test_tcp_oos.c
+++ b/test/unit/tcp/test_tcp_oos.c
@@ -471,7 +471,7 @@ START_TEST(test_tcp_recv_ooseq_overrun_rxwin)
   int datalen = 0;
   int datalen2;
 
-  for(i = 0; i < sizeof(data_full_wnd); i++) {
+  for(i = 0; i < (int)sizeof(data_full_wnd); i++) {
     data_full_wnd[i] = (char)i;
   }
 
@@ -840,7 +840,7 @@ static void test_tcp_recv_ooseq_double_FINs(int delay_packet)
   u32_t exp_rx_calls = 0, exp_rx_bytes = 0, exp_close_calls = 0, exp_oos_pbufs = 0, exp_oos_tcplen = 0;
   int first_dropped = 0xff;
 
-  for(i = 0; i < sizeof(data_full_wnd); i++) {
+  for(i = 0; i < (int)sizeof(data_full_wnd); i++) {
     data_full_wnd[i] = (char)i;
   }