diff --git a/test/unit/core/test_mem.c b/test/unit/core/test_mem.c
index 10574c05..66b4877e 100644
--- a/test/unit/core/test_mem.c
+++ b/test/unit/core/test_mem.c
@@ -61,9 +61,10 @@ static void malloc_keep_x(int x, int num, int size, int freestep)
 {
    int i;
    void* p[16];
+   LWIP_ASSERT("invalid size", size >= 0 && size < (mem_size_t)-1);
    memset(p, 0, sizeof(p));
    for(i = 0; i < num && i < 16; i++) {
-      p[i] = mem_malloc(size);
+      p[i] = mem_malloc((mem_size_t)size);
       fail_unless(p[i] != NULL);
    }
    for(i = 0; i < num && i < 16; i += freestep) {
diff --git a/test/unit/core/test_pbuf.c b/test/unit/core/test_pbuf.c
index 8711136c..bda583a7 100644
--- a/test/unit/core/test_pbuf.c
+++ b/test/unit/core/test_pbuf.c
@@ -93,12 +93,15 @@ START_TEST(test_pbuf_queueing_bigger_than_64k)
   struct pbuf *p1, *p2, *p3, *rest2=NULL, *rest3=NULL;
   LWIP_UNUSED_ARG(_i);
 
-  for(i = 0; i < TESTBUFSIZE_1; i++)
-    testbuf_1[i] = rand();
-  for(i = 0; i < TESTBUFSIZE_2; i++)
-    testbuf_2[i] = rand();
-  for(i = 0; i < TESTBUFSIZE_3; i++)
-    testbuf_3[i] = rand();
+  for(i = 0; i < TESTBUFSIZE_1; i++) {
+    testbuf_1[i] = (u8_t)rand();
+  }
+  for(i = 0; i < TESTBUFSIZE_2; i++) {
+    testbuf_2[i] = (u8_t)rand();
+  }
+  for(i = 0; i < TESTBUFSIZE_3; i++) {
+    testbuf_3[i] = (u8_t)rand();
+  }
 
   p1 = pbuf_alloc(PBUF_RAW, TESTBUFSIZE_1, PBUF_POOL);
   fail_unless(p1 != NULL);
@@ -151,6 +154,7 @@ START_TEST(test_pbuf_take_at_edge)
   u8_t testdata[] = { 0x01, 0x08, 0x82, 0x02 };
   struct pbuf *p = pbuf_alloc(PBUF_RAW, 1024, PBUF_POOL);
   struct pbuf *q = p->next;
+  LWIP_UNUSED_ARG(_i);
   /* alloc big enough to get a chain of pbufs */
   fail_if(p->tot_len == p->len);
   memset(p->payload, 0, p->len);
@@ -201,6 +205,7 @@ START_TEST(test_pbuf_get_put_at_edge)
   u8_t getdata;
   struct pbuf *p = pbuf_alloc(PBUF_RAW, 1024, PBUF_POOL);
   struct pbuf *q = p->next;
+  LWIP_UNUSED_ARG(_i);
   /* alloc big enough to get a chain of pbufs */
   fail_if(p->tot_len == p->len);
   memset(p->payload, 0, p->len);
diff --git a/test/unit/dhcp/test_dhcp.c b/test/unit/dhcp/test_dhcp.c
index dc33f370..2ceca097 100644
--- a/test/unit/dhcp/test_dhcp.c
+++ b/test/unit/dhcp/test_dhcp.c
@@ -136,10 +136,11 @@ static void tick_lwip(void)
   }
 }
 
-static void send_pkt(struct netif *netif, const u8_t *data, u32_t len)
+static void send_pkt(struct netif *netif, const u8_t *data, size_t len)
 {
-  struct pbuf *p = pbuf_alloc(PBUF_RAW, len, PBUF_POOL);
-  struct pbuf *q;
+  struct pbuf *p, *q;
+  LWIP_ASSERT("pkt too big", len <= 0xFFFF);
+  p = pbuf_alloc(PBUF_RAW, (u16_t)len, PBUF_POOL);
 
   if (debug) {
     /* Dump data */
@@ -879,7 +880,7 @@ START_TEST(test_dhcp_nak_no_endmarker)
   memcpy(&dhcp_offer[46], &xid, 4); /* insert correct transaction id */
   send_pkt(&net_test, dhcp_offer, sizeof(dhcp_offer));
   
-  fail_unless(net_test.dhcp->state == DHCP_REQUESTING);
+  fail_unless(net_test.dhcp->state == DHCP_STATE_REQUESTING);
 
   fail_unless(txpacket == 2); /* No more sent */
   xid = htonl(net_test.dhcp->xid); /* xid updated */
@@ -887,7 +888,7 @@ START_TEST(test_dhcp_nak_no_endmarker)
   send_pkt(&net_test, dhcp_nack_no_endmarker, sizeof(dhcp_nack_no_endmarker));
 
   /* NAK should put us in another state for a while, no other way detecting it */
-  fail_unless(net_test.dhcp->state != DHCP_REQUESTING);
+  fail_unless(net_test.dhcp->state != DHCP_STATE_REQUESTING);
 
   netif_remove(&net_test);
 }
diff --git a/test/unit/tcp/tcp_helper.c b/test/unit/tcp/tcp_helper.c
index 2493f234..74254696 100644
--- a/test/unit/tcp/tcp_helper.c
+++ b/test/unit/tcp/tcp_helper.c
@@ -47,6 +47,7 @@ tcp_create_segment_wnd(ip_addr_t* src_ip, ip_addr_t* dst_ip,
   struct ip_hdr* iphdr;
   struct tcp_hdr* tcphdr;
   u16_t pbuf_len = (u16_t)(sizeof(struct ip_hdr) + sizeof(struct tcp_hdr) + data_len);
+  LWIP_ASSERT("data_len too big", data_len <= 0xFFFF);
 
   p = pbuf_alloc(PBUF_RAW, pbuf_len, PBUF_POOL);
   EXPECT_RETNULL(p != NULL);
@@ -86,7 +87,7 @@ tcp_create_segment_wnd(ip_addr_t* src_ip, ip_addr_t* dst_ip,
     /* let p point to TCP data */
     pbuf_header(p, -(s16_t)sizeof(struct tcp_hdr));
     /* copy data */
-    pbuf_take(p, data, data_len);
+    pbuf_take(p, data, (u16_t)data_len);
     /* let p point to TCP header again */
     pbuf_header(p, sizeof(struct tcp_hdr));
   }