diff --git a/examples/deflate.c b/examples/deflate.c
index 4ba77b78..535e984b 100644
--- a/examples/deflate.c
+++ b/examples/deflate.c
@@ -132,7 +132,7 @@ static void deflate(nghttp2_hd_deflater *deflater,
   outlen = (size_t)rv;
 
   printf("\nDeflate (%zu byte(s), ratio %.02f):\n\n", outlen,
-         sum == 0 ? 0 : (double)outlen / sum);
+         sum == 0 ? 0 : (double)outlen / (double)sum);
 
   for (i = 0; i < outlen; ++i) {
     if ((i & 0x0fu) == 0) {
diff --git a/examples/libevent-client.c b/examples/libevent-client.c
index ecbd44f4..c3363070 100644
--- a/examples/libevent-client.c
+++ b/examples/libevent-client.c
@@ -120,7 +120,7 @@ static http2_stream_data *create_http2_stream_data(const char *uri,
   }
   if (u->field_set & (1 << UF_QUERY)) {
     /* +1 for '?' character */
-    stream_data->pathlen += u->field_data[UF_QUERY].len + 1;
+    stream_data->pathlen += (size_t)(u->field_data[UF_QUERY].len + 1);
   }
 
   stream_data->path = malloc(stream_data->pathlen);
diff --git a/examples/libevent-server.c b/examples/libevent-server.c
index 8432bea7..cc82a1c5 100644
--- a/examples/libevent-server.c
+++ b/examples/libevent-server.c
@@ -312,13 +312,13 @@ static int ends_with(const char *s, const char *sub) {
 /* Returns int value of hex string character |c| */
 static uint8_t hex_to_uint(uint8_t c) {
   if ('0' <= c && c <= '9') {
-    return c - '0';
+    return (uint8_t)(c - '0');
   }
   if ('A' <= c && c <= 'F') {
-    return c - 'A' + 10;
+    return (uint8_t)(c - 'A' + 10);
   }
   if ('a' <= c && c <= 'f') {
-    return c - 'a' + 10;
+    return (uint8_t)(c - 'a' + 10);
   }
   return 0;
 }
@@ -340,7 +340,7 @@ static char *percent_decode(const uint8_t *value, size_t valuelen) {
         continue;
       }
       res[j++] =
-          (char)(hex_to_uint(value[i + 1]) << 4) + hex_to_uint(value[i + 2]);
+          (char)((hex_to_uint(value[i + 1]) << 4) + hex_to_uint(value[i + 2]));
       i += 3;
     }
     memcpy(&res[j], &value[i], 2);
diff --git a/examples/tiny-nghttpd.c b/examples/tiny-nghttpd.c
index db54a553..6cb95694 100644
--- a/examples/tiny-nghttpd.c
+++ b/examples/tiny-nghttpd.c
@@ -248,7 +248,7 @@ static char *cpydig(char *buf, int n, size_t len) {
 
   p = buf + len - 1;
   do {
-    *p-- = (n % 10) + '0';
+    *p-- = (char)((n % 10) + '0');
     n /= 10;
   } while (p >= buf);
 
@@ -319,7 +319,7 @@ static size_t utos(char *buf, size_t len, uint64_t n) {
 
   buf += nwrite - 1;
   do {
-    *buf-- = (n % 10) + '0';
+    *buf-- = (char)((n % 10) + '0');
     n /= 10;
   } while (n);
 
diff --git a/lib/nghttp2_buf.h b/lib/nghttp2_buf.h
index 6266cce9..8977f2ea 100644
--- a/lib/nghttp2_buf.h
+++ b/lib/nghttp2_buf.h
@@ -300,12 +300,15 @@ int nghttp2_bufs_orb_hold(nghttp2_bufs *bufs, uint8_t b);
 
 #define nghttp2_bufs_fast_orb(BUFS, B)                                         \
   do {                                                                         \
-    *(BUFS)->cur->buf.last++ |= B;                                             \
+    uint8_t **p = &(BUFS)->cur->buf.last;                                      \
+    **p = (uint8_t)(**p | (B));                                                \
+    ++(*p);                                                                    \
   } while (0)
 
 #define nghttp2_bufs_fast_orb_hold(BUFS, B)                                    \
   do {                                                                         \
-    *(BUFS)->cur->buf.last |= B;                                               \
+    uint8_t *p = (BUFS)->cur->buf.last;                                        \
+    *p = (uint8_t)(*p | (B));                                                  \
   } while (0)
 
 /*
diff --git a/lib/nghttp2_frame.c b/lib/nghttp2_frame.c
index 3f1f37cd..de491205 100644
--- a/lib/nghttp2_frame.c
+++ b/lib/nghttp2_frame.c
@@ -219,7 +219,7 @@ static int frame_pack_headers_shared(nghttp2_bufs *bufs,
      CONTINUATION frame is involved. Remove END_HEADERS flag from the
      first frame. */
   if (bufs->head != bufs->cur) {
-    hd.flags &= ~NGHTTP2_FLAG_END_HEADERS;
+    hd.flags = (uint8_t)(hd.flags & ~NGHTTP2_FLAG_END_HEADERS);
   }
 
   buf->pos -= NGHTTP2_FRAME_HDLEN;
diff --git a/lib/nghttp2_hd.c b/lib/nghttp2_hd.c
index f8ef09bd..ea9a1d77 100644
--- a/lib/nghttp2_hd.c
+++ b/lib/nghttp2_hd.c
@@ -506,7 +506,7 @@ int nghttp2_hd_entry_init(nghttp2_hd_entry *ent, uint8_t flags, uint8_t *name,
   if ((flags & NGHTTP2_HD_FLAG_NAME_ALLOC) &&
       (flags & NGHTTP2_HD_FLAG_NAME_GIFT) == 0) {
     if (namelen == 0) {
-      flags &= ~NGHTTP2_HD_FLAG_NAME_ALLOC;
+      flags = (uint8_t)(flags & ~NGHTTP2_HD_FLAG_NAME_ALLOC);
       ent->nv.name = (uint8_t *)"";
     } else {
       /* copy including terminating NULL byte */
@@ -522,7 +522,7 @@ int nghttp2_hd_entry_init(nghttp2_hd_entry *ent, uint8_t flags, uint8_t *name,
   if ((flags & NGHTTP2_HD_FLAG_VALUE_ALLOC) &&
       (flags & NGHTTP2_HD_FLAG_VALUE_GIFT) == 0) {
     if (valuelen == 0) {
-      flags &= ~NGHTTP2_HD_FLAG_VALUE_ALLOC;
+      flags = (uint8_t)(flags & ~NGHTTP2_HD_FLAG_VALUE_ALLOC);
       ent->nv.value = (uint8_t *)"";
     } else {
       /* copy including terminating NULL byte */
@@ -877,7 +877,7 @@ static int emit_literal_header(nghttp2_nv *nv_out, int *token_out,
 }
 
 static size_t count_encoded_length(size_t n, size_t prefix) {
-  size_t k = (1 << prefix) - 1;
+  size_t k = (size_t)((1 << prefix) - 1);
   size_t len = 0;
 
   if (n < k) {
@@ -894,21 +894,23 @@ static size_t count_encoded_length(size_t n, size_t prefix) {
 }
 
 static size_t encode_length(uint8_t *buf, size_t n, size_t prefix) {
-  size_t k = (1 << prefix) - 1;
+  size_t k = (size_t)((1 << prefix) - 1);
   uint8_t *begin = buf;
 
-  *buf &= ~k;
+  *buf = (uint8_t)(*buf & ~k);
 
   if (n < k) {
-    *buf |= n;
+    *buf = (uint8_t)(*buf | n);
     return 1;
   }
 
-  *buf++ |= k;
+  *buf = (uint8_t)(*buf | k);
+  ++buf;
+
   n -= k;
 
   for (; n >= 128; n >>= 7) {
-    *buf++ = (1 << 7) | (n & 0x7f);
+    *buf++ = (uint8_t)((1 << 7) | (n & 0x7f));
   }
 
   *buf++ = (uint8_t)n;
@@ -936,7 +938,7 @@ static size_t encode_length(uint8_t *buf, size_t n, size_t prefix) {
 static ssize_t decode_length(uint32_t *res, size_t *shift_ptr, int *final,
                              uint32_t initial, size_t shift, uint8_t *in,
                              uint8_t *last, size_t prefix) {
-  uint32_t k = (1 << prefix) - 1;
+  uint32_t k = (uint8_t)((1 << prefix) - 1);
   uint32_t n = initial;
   uint8_t *start = in;
 
diff --git a/lib/nghttp2_hd_huffman.c b/lib/nghttp2_hd_huffman.c
index f2184dde..fb2d167b 100644
--- a/lib/nghttp2_hd_huffman.c
+++ b/lib/nghttp2_hd_huffman.c
@@ -48,17 +48,17 @@ static ssize_t huff_encode_sym(nghttp2_bufs *bufs, size_t *avail_ptr,
 
   /* We assume that sym->nbits <= 32 */
   if (rembits > nbits) {
-    nghttp2_bufs_fast_orb_hold(bufs, code << (rembits - nbits));
+    nghttp2_bufs_fast_orb_hold(bufs, (uint8_t)(code << (rembits - nbits)));
     return (ssize_t)(rembits - nbits);
   }
 
   if (rembits == nbits) {
-    nghttp2_bufs_fast_orb(bufs, code);
+    nghttp2_bufs_fast_orb(bufs, (uint8_t)code);
     --*avail_ptr;
     return 8;
   }
 
-  nghttp2_bufs_fast_orb(bufs, code >> (nbits - rembits));
+  nghttp2_bufs_fast_orb(bufs, (uint8_t)(code >> (nbits - rembits)));
   --*avail_ptr;
 
   nbits -= rembits;
@@ -87,7 +87,7 @@ static ssize_t huff_encode_sym(nghttp2_bufs *bufs, size_t *avail_ptr,
 
   /* handle longer code path */
   if (nbits > 24) {
-    nghttp2_bufs_fast_addb(bufs, code >> 24);
+    nghttp2_bufs_fast_addb(bufs, (uint8_t)(code >> 24));
     nbits -= 8;
   }
 
@@ -157,7 +157,7 @@ int nghttp2_hd_huff_encode(nghttp2_bufs *bufs, const uint8_t *src,
     const nghttp2_huff_sym *sym = &huff_sym_table[256];
     assert(avail);
     /* Caution we no longer adjust avail here */
-    nghttp2_bufs_fast_orb(bufs, sym->code >> (sym->nbits - rembits));
+    nghttp2_bufs_fast_orb(bufs, (uint8_t)(sym->code >> (sym->nbits - rembits)));
   }
 
   return 0;
diff --git a/lib/nghttp2_http.c b/lib/nghttp2_http.c
index 05cca76f..5dfd44fc 100644
--- a/lib/nghttp2_http.c
+++ b/lib/nghttp2_http.c
@@ -32,7 +32,7 @@
 #include "nghttp2_helper.h"
 
 static uint8_t downcase(uint8_t c) {
-  return 'A' <= c && c <= 'Z' ? (c - 'A' + 'a') : c;
+  return 'A' <= c && c <= 'Z' ? (uint8_t)(c - 'A' + 'a') : c;
 }
 
 static int memieq(const void *a, const void *b, size_t n) {
@@ -90,7 +90,7 @@ static int check_pseudo_header(nghttp2_stream *stream, const nghttp2_nv *nv,
   if (lws(nv->value, nv->valuelen)) {
     return 0;
   }
-  stream->http_flags |= flag;
+  stream->http_flags = (uint16_t)(stream->http_flags | flag);
   return 1;
 }
 
@@ -368,14 +368,16 @@ int nghttp2_http_on_response_headers(nghttp2_stream *stream) {
 
   if (stream->status_code / 100 == 1) {
     /* non-final response */
-    stream->http_flags = (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_ALL) |
-                         NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE;
+    stream->http_flags =
+        (uint16_t)((stream->http_flags & NGHTTP2_HTTP_FLAG_METH_ALL) |
+                   NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE);
     stream->content_length = -1;
     stream->status_code = -1;
     return 0;
   }
 
-  stream->http_flags &= ~NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE;
+  stream->http_flags =
+      (uint16_t)(stream->http_flags & ~NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE);
 
   if (!expect_response_body(stream)) {
     stream->content_length = 0;
@@ -409,7 +411,7 @@ int nghttp2_http_on_remote_end_stream(nghttp2_stream *stream) {
 }
 
 int nghttp2_http_on_data_chunk(nghttp2_stream *stream, size_t n) {
-  stream->recv_content_length += n;
+  stream->recv_content_length += (int64_t)n;
 
   if ((stream->http_flags & NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE) ||
       (stream->content_length != -1 &&
diff --git a/lib/nghttp2_npn.c b/lib/nghttp2_npn.c
index a8bdb237..91fca06c 100644
--- a/lib/nghttp2_npn.c
+++ b/lib/nghttp2_npn.c
@@ -30,7 +30,7 @@ static int select_next_protocol(unsigned char **out, unsigned char *outlen,
                                 const unsigned char *in, unsigned int inlen,
                                 const char *key, unsigned int keylen) {
   unsigned int i;
-  for (i = 0; i + keylen <= inlen; i += in [i] + 1) {
+  for (i = 0; i + keylen <= inlen; i += (unsigned int)(in [i] + 1)) {
     if (memcmp(&in[i], key, keylen) == 0) {
       *out = (unsigned char *)&in[i + 1];
       *outlen = in[i];
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index 5d38bb67..8d60f6eb 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -2276,7 +2276,7 @@ static int session_after_frame_sent1(nghttp2_session *session) {
         break;
       }
       case NGHTTP2_HCAT_PUSH_RESPONSE:
-        stream->flags &= ~NGHTTP2_STREAM_FLAG_PUSH;
+        stream->flags = (uint8_t)(stream->flags & ~NGHTTP2_STREAM_FLAG_PUSH);
         ++session->num_outgoing_streams;
       /* Fall through */
       case NGHTTP2_HCAT_RESPONSE:
@@ -2372,9 +2372,9 @@ static int session_after_frame_sent1(nghttp2_session *session) {
     /* We update flow control window after a frame was completely
        sent. This is possible because we choose payload length not to
        exceed the window */
-    session->remote_window_size -= frame->hd.length;
+    session->remote_window_size -= (int32_t)frame->hd.length;
     if (stream) {
-      stream->remote_window_size -= frame->hd.length;
+      stream->remote_window_size -= (int32_t)frame->hd.length;
     }
 
     if (stream && aux_data->eof) {
@@ -4374,7 +4374,7 @@ static int adjust_recv_window_size(int32_t *recv_window_size_ptr, size_t delta,
       *recv_window_size_ptr > NGHTTP2_MAX_WINDOW_SIZE - (int32_t)delta) {
     return -1;
   }
-  *recv_window_size_ptr += delta;
+  *recv_window_size_ptr += (int32_t)delta;
   return 0;
 }
 
@@ -4474,7 +4474,7 @@ static int session_update_consumed_size(nghttp2_session *session,
                                              NGHTTP2_FLOW_CONTROL_ERROR);
   }
 
-  *consumed_size_ptr += delta_size;
+  *consumed_size_ptr += (int32_t)delta_size;
 
   /* recv_window_size may be smaller than consumed_size, because it
      may be decreased by negative value with
@@ -4681,7 +4681,7 @@ static ssize_t inbound_frame_compute_pad(nghttp2_inbound_frame *iframe) {
   size_t padlen;
 
   /* 1 for Pad Length field */
-  padlen = iframe->sbuf.pos[0] + 1;
+  padlen = (size_t)(iframe->sbuf.pos[0] + 1);
 
   DEBUGF(fprintf(stderr, "recv: padlen=%zu\n", padlen));
 
@@ -5580,7 +5580,8 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
 
       /* CONTINUATION won't bear NGHTTP2_PADDED flag */
 
-      iframe->frame.hd.flags |= cont_hd.flags & NGHTTP2_FLAG_END_HEADERS;
+      iframe->frame.hd.flags = (uint8_t)(
+          iframe->frame.hd.flags | (cont_hd.flags & NGHTTP2_FLAG_END_HEADERS));
       iframe->frame.hd.length += cont_hd.length;
 
       busy = 1;
diff --git a/lib/nghttp2_stream.c b/lib/nghttp2_stream.c
index 1959e96d..e8dfd0c2 100644
--- a/lib/nghttp2_stream.c
+++ b/lib/nghttp2_stream.c
@@ -89,7 +89,7 @@ void nghttp2_stream_free(nghttp2_stream *stream) {
 }
 
 void nghttp2_stream_shutdown(nghttp2_stream *stream, nghttp2_shut_flag flag) {
-  stream->shut_flags |= flag;
+  stream->shut_flags = (uint8_t)(stream->shut_flags | flag);
 }
 
 /*
@@ -424,7 +424,7 @@ int nghttp2_stream_detach_item(nghttp2_stream *stream) {
                  stream->stream_id, stream->item));
 
   stream->item = NULL;
-  stream->flags &= ~NGHTTP2_STREAM_FLAG_DEFERRED_ALL;
+  stream->flags = (uint8_t)(stream->flags & ~NGHTTP2_STREAM_FLAG_DEFERRED_ALL);
 
   return stream_update_dep_on_detach_item(stream);
 }
@@ -446,7 +446,7 @@ int nghttp2_stream_resume_deferred_item(nghttp2_stream *stream, uint8_t flags) {
   DEBUGF(fprintf(stderr, "stream: stream=%d resume item=%p flags=%02x\n",
                  stream->stream_id, stream->item, flags));
 
-  stream->flags &= ~flags;
+  stream->flags = (uint8_t)(stream->flags & ~flags);
 
   if (stream->flags & NGHTTP2_STREAM_FLAG_DEFERRED_ALL) {
     return 0;
@@ -495,7 +495,7 @@ int nghttp2_stream_update_local_initial_window_size(
 
 void nghttp2_stream_promise_fulfilled(nghttp2_stream *stream) {
   stream->state = NGHTTP2_STREAM_OPENED;
-  stream->flags &= ~NGHTTP2_STREAM_FLAG_PUSH;
+  stream->flags = (uint8_t)(stream->flags & ~NGHTTP2_STREAM_FLAG_PUSH);
 }
 
 int nghttp2_stream_dep_find_ancestor(nghttp2_stream *stream,
diff --git a/lib/nghttp2_submit.c b/lib/nghttp2_submit.c
index fb7d1c00..14ec7666 100644
--- a/lib/nghttp2_submit.c
+++ b/lib/nghttp2_submit.c
@@ -71,8 +71,9 @@ static int32_t submit_headers_shared(nghttp2_session *session, uint8_t flags,
   item->aux_data.headers.stream_user_data = stream_user_data;
   item->aux_data.headers.attach_stream = attach_stream;
 
-  flags_copy = (flags & (NGHTTP2_FLAG_END_STREAM | NGHTTP2_FLAG_PRIORITY)) |
-               NGHTTP2_FLAG_END_HEADERS;
+  flags_copy =
+      (uint8_t)((flags & (NGHTTP2_FLAG_END_STREAM | NGHTTP2_FLAG_PRIORITY)) |
+                NGHTTP2_FLAG_END_HEADERS);
 
   if (stream_id == -1) {
     if (session->next_stream_id > INT32_MAX) {
diff --git a/tests/nghttp2_frame_test.c b/tests/nghttp2_frame_test.c
index ecf8a2c4..06d83448 100644
--- a/tests/nghttp2_frame_test.c
+++ b/tests/nghttp2_frame_test.c
@@ -487,7 +487,7 @@ void test_nghttp2_nv_array_copy(void) {
   CU_ASSERT(0 == rv);
   CU_ASSERT(nva[0].namelen == 5);
   CU_ASSERT(0 == memcmp("alpha", nva[0].name, 5));
-  CU_ASSERT(nva[0].valuelen = 5);
+  CU_ASSERT(nva[0].valuelen == 5);
   CU_ASSERT(0 == memcmp("bravo", nva[0].value, 5));
   CU_ASSERT(nva[1].namelen == 7);
   CU_ASSERT(0 == memcmp("charlie", nva[1].name, 7));
diff --git a/tests/nghttp2_hd_test.c b/tests/nghttp2_hd_test.c
index 308f3615..3eb0b42c 100644
--- a/tests/nghttp2_hd_test.c
+++ b/tests/nghttp2_hd_test.c
@@ -1201,21 +1201,24 @@ void test_nghttp2_hd_public_api(void) {
 }
 
 static size_t encode_length(uint8_t *buf, uint64_t n, size_t prefix) {
-  size_t k = (1 << prefix) - 1;
+  size_t k = (size_t)((1 << prefix) - 1);
   size_t len = 0;
-  *buf &= ~k;
+  *buf = (uint8_t)(*buf & ~k);
   if (n >= k) {
-    *buf++ |= k;
+    *buf = (uint8_t)(*buf | k);
+    ++buf;
     n -= k;
     ++len;
   } else {
-    *buf++ |= n;
+    *buf = (uint8_t)(*buf | n);
+    ++buf;
     return 1;
   }
   do {
     ++len;
     if (n >= 128) {
-      *buf++ = (1 << 7) | (n & 0x7f);
+      *buf = (uint8_t)((1 << 7) | (n & 0x7f));
+      ++buf;
       n >>= 7;
     } else {
       *buf++ = (uint8_t)n;
diff --git a/tests/nghttp2_session_test.c b/tests/nghttp2_session_test.c
index 645a849f..ed52d322 100644
--- a/tests/nghttp2_session_test.c
+++ b/tests/nghttp2_session_test.c
@@ -328,7 +328,7 @@ static int send_data_callback(nghttp2_session *session _U_,
   acc->length += NGHTTP2_FRAME_HDLEN;
 
   if (frame->data.padlen) {
-    *(acc->buf + acc->length++) = (uint8_t)frame->data.padlen - 1;
+    *(acc->buf + acc->length++) = (uint8_t)(frame->data.padlen - 1);
   }
 
   acc->length += length;
@@ -927,7 +927,7 @@ void test_nghttp2_session_recv_continuation(void) {
   datalen = NGHTTP2_FRAME_HDLEN + 1;
   buf->pos += NGHTTP2_FRAME_HDLEN + 1;
 
-  nghttp2_put_uint32be(data, (1 << 8) + data[3]);
+  nghttp2_put_uint32be(data, (uint32_t)((1 << 8) + data[3]));
 
   /* First CONTINUATION, 2 bytes */
   nghttp2_frame_hd_init(&cont_hd, 2, NGHTTP2_CONTINUATION, NGHTTP2_FLAG_NONE,
@@ -1099,7 +1099,7 @@ void test_nghttp2_session_recv_headers_with_priority(void) {
   buf = &bufs.head->buf;
   /* Make payload shorter than required length to store priority
      group */
-  nghttp2_put_uint32be(buf->pos, (4 << 8) + buf->pos[3]);
+  nghttp2_put_uint32be(buf->pos, (uint32_t)((4 << 8) + buf->pos[3]));
 
   ud.frame_recv_cb_called = 0;