diff --git a/lib/nghttp2_frame.c b/lib/nghttp2_frame.c
index 90efaff5..210df058 100644
--- a/lib/nghttp2_frame.c
+++ b/lib/nghttp2_frame.c
@@ -672,6 +672,9 @@ int nghttp2_frame_pack_altsvc(nghttp2_bufs *bufs, nghttp2_extension *frame) {
   nghttp2_buf *buf;
   nghttp2_ext_altsvc *altsvc;
 
+  /* This is required with --disable-assert. */
+  (void)rv;
+
   altsvc = frame->payload;
 
   buf = &bufs->head->buf;
diff --git a/src/h2load_http2_session.cc b/src/h2load_http2_session.cc
index f7f63f17..4419fe8e 100644
--- a/src/h2load_http2_session.cc
+++ b/src/h2load_http2_session.cc
@@ -180,6 +180,9 @@ ssize_t send_callback(nghttp2_session *session, const uint8_t *data,
 void Http2Session::on_connect() {
   int rv;
 
+  // This is required with --disable-assert.
+  (void)rv;
+
   nghttp2_session_callbacks *callbacks;
 
   nghttp2_session_callbacks_new(&callbacks);
diff --git a/src/nghttp.cc b/src/nghttp.cc
index 84b0ddda..2aec0eda 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -172,6 +172,8 @@ Request::~Request() { nghttp2_gzip_inflate_del(inflater); }
 
 void Request::init_inflater() {
   int rv;
+  // This is required with --disable-assert.
+  (void)rv;
   rv = nghttp2_gzip_inflate_new(&inflater);
   assert(rv == 0);
 }
diff --git a/src/nghttp2_gzip_test.c b/src/nghttp2_gzip_test.c
index 4255caa9..7ad3c8d2 100644
--- a/src/nghttp2_gzip_test.c
+++ b/src/nghttp2_gzip_test.c
@@ -43,14 +43,14 @@ static size_t deflate_data(uint8_t *out, size_t outlen, const uint8_t *in,
   zst.opaque = Z_NULL;
 
   rv = deflateInit(&zst, Z_DEFAULT_COMPRESSION);
-  assert(rv == Z_OK);
+  CU_ASSERT(rv == Z_OK);
 
   zst.avail_in = (unsigned int)inlen;
   zst.next_in = (uint8_t *)in;
   zst.avail_out = (unsigned int)outlen;
   zst.next_out = out;
   rv = deflate(&zst, Z_SYNC_FLUSH);
-  assert(rv == Z_OK);
+  CU_ASSERT(rv == Z_OK);
 
   deflateEnd(&zst);
 
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index c33f8c51..d1e44f16 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -3613,6 +3613,7 @@ StringRef strproto(shrpx_proto proto) {
 
   // gcc needs this.
   assert(0);
+  abort();
 }
 
 namespace {
diff --git a/src/shrpx_config_test.cc b/src/shrpx_config_test.cc
index bc168b40..75319712 100644
--- a/src/shrpx_config_test.cc
+++ b/src/shrpx_config_test.cc
@@ -163,14 +163,14 @@ void test_shrpx_config_parse_log_format(void) {
 void test_shrpx_config_read_tls_ticket_key_file(void) {
   char file1[] = "/tmp/nghttpx-unittest.XXXXXX";
   auto fd1 = mkstemp(file1);
-  assert(fd1 != -1);
-  assert(48 ==
-         write(fd1, "0..............12..............34..............5", 48));
+  CU_ASSERT(fd1 != -1);
+  CU_ASSERT(48 ==
+            write(fd1, "0..............12..............34..............5", 48));
   char file2[] = "/tmp/nghttpx-unittest.XXXXXX";
   auto fd2 = mkstemp(file2);
-  assert(fd2 != -1);
-  assert(48 ==
-         write(fd2, "6..............78..............9a..............b", 48));
+  CU_ASSERT(fd2 != -1);
+  CU_ASSERT(48 ==
+            write(fd2, "6..............78..............9a..............b", 48));
 
   close(fd1);
   close(fd2);
@@ -204,16 +204,18 @@ void test_shrpx_config_read_tls_ticket_key_file(void) {
 void test_shrpx_config_read_tls_ticket_key_file_aes_256(void) {
   char file1[] = "/tmp/nghttpx-unittest.XXXXXX";
   auto fd1 = mkstemp(file1);
-  assert(fd1 != -1);
-  assert(80 == write(fd1, "0..............12..............................34..."
-                          "...........................5",
-                     80));
+  CU_ASSERT(fd1 != -1);
+  CU_ASSERT(80 == write(fd1,
+                        "0..............12..............................34..."
+                        "...........................5",
+                        80));
   char file2[] = "/tmp/nghttpx-unittest.XXXXXX";
   auto fd2 = mkstemp(file2);
-  assert(fd2 != -1);
-  assert(80 == write(fd2, "6..............78..............................9a..."
-                          "...........................b",
-                     80));
+  CU_ASSERT(fd2 != -1);
+  CU_ASSERT(80 == write(fd2,
+                        "6..............78..............................9a..."
+                        "...........................b",
+                        80));
 
   close(fd1);
   close(fd2);
diff --git a/src/shrpx_dns_resolver.cc b/src/shrpx_dns_resolver.cc
index 356fd970..cb77e604 100644
--- a/src/shrpx_dns_resolver.cc
+++ b/src/shrpx_dns_resolver.cc
@@ -204,6 +204,7 @@ int DNSResolver::handle_event(int rfd, int wfd) {
   default:
     // Unreachable
     assert(0);
+    abort();
   }
 }
 
diff --git a/src/shrpx_dns_tracker.cc b/src/shrpx_dns_tracker.cc
index 9eeca5d8..1ab368e3 100644
--- a/src/shrpx_dns_tracker.cc
+++ b/src/shrpx_dns_tracker.cc
@@ -250,6 +250,7 @@ int DNSTracker::resolve(Address *result, DNSQuery *dnsq) {
     return DNS_STATUS_OK;
   default:
     assert(0);
+    abort();
   }
 }
 
diff --git a/src/shrpx_downstream_queue.cc b/src/shrpx_downstream_queue.cc
index f7f66b7d..74465396 100644
--- a/src/shrpx_downstream_queue.cc
+++ b/src/shrpx_downstream_queue.cc
@@ -158,6 +158,8 @@ Downstream *DownstreamQueue::remove_and_get_blocked(Downstream *downstream,
 
   auto next_downstream = link->downstream;
   auto link2 = next_downstream->detach_blocked_link();
+  // This is required with --disable-assert.
+  (void)link2;
   assert(link2 == link);
   ent.blocked.remove(link);
   delete link;
diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index 56876738..539edfed 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -334,6 +334,7 @@ int Http2Session::resolve_name() {
     return 0;
   default:
     assert(0);
+    abort();
   }
 }
 
@@ -2115,7 +2116,10 @@ int Http2Session::write_tls() {
   for (;;) {
     if (wb_.rleft() > 0) {
       auto iovcnt = wb_.riovec(&iov, 1);
-      assert(iovcnt == 1);
+      if (iovcnt != 1) {
+        assert(0);
+        return -1;
+      }
       auto nwrite = conn_.write_tls(iov.iov_base, iov.iov_len);
 
       if (nwrite == 0) {
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 561fcbe3..03b8f771 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -1307,7 +1307,10 @@ int HttpDownstreamConnection::write_tls() {
 
   while (input->rleft() > 0) {
     auto iovcnt = input->riovec(&iov, 1);
-    assert(iovcnt == 1);
+    if (iovcnt != 1) {
+      assert(0);
+      return -1;
+    }
     auto nwrite = conn_.write_tls(iov.iov_base, iov.iov_len);
 
     if (nwrite == 0) {
diff --git a/src/shrpx_live_check.cc b/src/shrpx_live_check.cc
index 4203b0ae..863ffa51 100644
--- a/src/shrpx_live_check.cc
+++ b/src/shrpx_live_check.cc
@@ -478,7 +478,10 @@ int LiveCheck::write_tls() {
   for (;;) {
     if (wb_.rleft() > 0) {
       auto iovcnt = wb_.riovec(&iov, 1);
-      assert(iovcnt == 1);
+      if (iovcnt != 1) {
+        assert(0);
+        return -1;
+      }
       auto nwrite = conn_.write_tls(iov.iov_base, iov.iov_len);
 
       if (nwrite == 0) {
@@ -544,7 +547,10 @@ int LiveCheck::write_clear() {
   for (;;) {
     if (wb_.rleft() > 0) {
       auto iovcnt = wb_.riovec(&iov, 1);
-      assert(iovcnt == 1);
+      if (iovcnt != 1) {
+        assert(0);
+        return -1;
+      }
       auto nwrite = conn_.write_clear(iov.iov_base, iov.iov_len);
 
       if (nwrite == 0) {