diff --git a/src/http/modules/ngx_http_auth_basic_module.c b/src/http/modules/ngx_http_auth_basic_module.c
index ed9df3430..4e28b6ce6 100644
--- a/src/http/modules/ngx_http_auth_basic_module.c
+++ b/src/http/modules/ngx_http_auth_basic_module.c
@@ -357,6 +357,8 @@ ngx_http_auth_basic_create_loc_conf(ngx_conf_t *cf)
         return NULL;
     }
 
+    conf->realm = NGX_CONF_UNSET_PTR;
+
     return conf;
 }
 
@@ -367,9 +369,7 @@ ngx_http_auth_basic_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_http_auth_basic_loc_conf_t  *prev = parent;
     ngx_http_auth_basic_loc_conf_t  *conf = child;
 
-    if (conf->realm == NULL) {
-        conf->realm = prev->realm;
-    }
+    ngx_conf_merge_ptr_value(conf->realm, prev->realm, NULL);
 
     if (conf->user_file.value.data == NULL) {
         conf->user_file = prev->user_file;
diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
index 53bc54710..8db35631c 100644
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -4331,7 +4331,6 @@ ngx_http_grpc_create_loc_conf(ngx_conf_t *cf)
      *     conf->upstream.ignore_headers = 0;
      *     conf->upstream.next_upstream = 0;
      *     conf->upstream.hide_headers_hash = { NULL, 0 };
-     *     conf->upstream.ssl_name = NULL;
      *
      *     conf->headers.lengths = NULL;
      *     conf->headers.values = NULL;
@@ -4364,6 +4363,7 @@ ngx_http_grpc_create_loc_conf(ngx_conf_t *cf)
 
 #if (NGX_HTTP_SSL)
     conf->upstream.ssl_session_reuse = NGX_CONF_UNSET;
+    conf->upstream.ssl_name = NGX_CONF_UNSET_PTR;
     conf->upstream.ssl_server_name = NGX_CONF_UNSET;
     conf->upstream.ssl_verify = NGX_CONF_UNSET;
     conf->ssl_verify_depth = NGX_CONF_UNSET_UINT;
@@ -4459,10 +4459,8 @@ ngx_http_grpc_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_str_value(conf->ssl_ciphers, prev->ssl_ciphers,
                              "DEFAULT");
 
-    if (conf->upstream.ssl_name == NULL) {
-        conf->upstream.ssl_name = prev->upstream.ssl_name;
-    }
-
+    ngx_conf_merge_ptr_value(conf->upstream.ssl_name,
+                              prev->upstream.ssl_name, NULL);
     ngx_conf_merge_value(conf->upstream.ssl_server_name,
                               prev->upstream.ssl_server_name, 0);
     ngx_conf_merge_value(conf->upstream.ssl_verify,
diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index a63c3ed54..97c168b45 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -3327,9 +3327,7 @@ ngx_http_proxy_create_loc_conf(ngx_conf_t *cf)
      *     conf->upstream.hide_headers_hash = { NULL, 0 };
      *     conf->upstream.store_lengths = NULL;
      *     conf->upstream.store_values = NULL;
-     *     conf->upstream.ssl_name = NULL;
      *
-     *     conf->method = NULL;
      *     conf->location = NULL;
      *     conf->url = { 0, NULL };
      *     conf->headers.lengths = NULL;
@@ -3400,6 +3398,7 @@ ngx_http_proxy_create_loc_conf(ngx_conf_t *cf)
 
 #if (NGX_HTTP_SSL)
     conf->upstream.ssl_session_reuse = NGX_CONF_UNSET;
+    conf->upstream.ssl_name = NGX_CONF_UNSET_PTR;
     conf->upstream.ssl_server_name = NGX_CONF_UNSET;
     conf->upstream.ssl_verify = NGX_CONF_UNSET;
     conf->ssl_verify_depth = NGX_CONF_UNSET_UINT;
@@ -3410,10 +3409,13 @@ ngx_http_proxy_create_loc_conf(ngx_conf_t *cf)
     /* "proxy_cyclic_temp_file" is disabled */
     conf->upstream.cyclic_temp_file = 0;
 
+    conf->upstream.change_buffering = 1;
+
     conf->headers_source = NGX_CONF_UNSET_PTR;
 
+    conf->method = NGX_CONF_UNSET_PTR;
+
     conf->redirect = NGX_CONF_UNSET;
-    conf->upstream.change_buffering = 1;
 
     conf->cookie_domains = NGX_CONF_UNSET_PTR;
     conf->cookie_paths = NGX_CONF_UNSET_PTR;
@@ -3708,10 +3710,6 @@ ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
 
 #endif
 
-    if (conf->method == NULL) {
-        conf->method = prev->method;
-    }
-
     ngx_conf_merge_value(conf->upstream.pass_request_headers,
                               prev->upstream.pass_request_headers, 1);
     ngx_conf_merge_value(conf->upstream.pass_request_body,
@@ -3732,10 +3730,8 @@ ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_str_value(conf->ssl_ciphers, prev->ssl_ciphers,
                              "DEFAULT");
 
-    if (conf->upstream.ssl_name == NULL) {
-        conf->upstream.ssl_name = prev->upstream.ssl_name;
-    }
-
+    ngx_conf_merge_ptr_value(conf->upstream.ssl_name,
+                              prev->upstream.ssl_name, NULL);
     ngx_conf_merge_value(conf->upstream.ssl_server_name,
                               prev->upstream.ssl_server_name, 0);
     ngx_conf_merge_value(conf->upstream.ssl_verify,
@@ -3761,6 +3757,8 @@ ngx_http_proxy_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
 
 #endif
 
+    ngx_conf_merge_ptr_value(conf->method, prev->method, NULL);
+
     ngx_conf_merge_value(conf->redirect, prev->redirect, 1);
 
     if (conf->redirect) {
diff --git a/src/http/modules/ngx_http_secure_link_module.c b/src/http/modules/ngx_http_secure_link_module.c
index 536e09a72..4d4ce6af1 100644
--- a/src/http/modules/ngx_http_secure_link_module.c
+++ b/src/http/modules/ngx_http_secure_link_module.c
@@ -302,11 +302,12 @@ ngx_http_secure_link_create_conf(ngx_conf_t *cf)
     /*
      * set by ngx_pcalloc():
      *
-     *     conf->variable = NULL;
-     *     conf->md5 = NULL;
      *     conf->secret = { 0, NULL };
      */
 
+    conf->variable = NGX_CONF_UNSET_PTR;
+    conf->md5 = NGX_CONF_UNSET_PTR;
+
     return conf;
 }
 
@@ -318,6 +319,9 @@ ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_http_secure_link_conf_t *conf = child;
 
     if (conf->secret.data) {
+        ngx_conf_init_ptr_value(conf->variable, NULL);
+        ngx_conf_init_ptr_value(conf->md5, NULL);
+
         if (conf->variable || conf->md5) {
             ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
                                "\"secure_link_secret\" cannot be mixed with "
@@ -328,13 +332,8 @@ ngx_http_secure_link_merge_conf(ngx_conf_t *cf, void *parent, void *child)
         return NGX_CONF_OK;
     }
 
-    if (conf->variable == NULL) {
-        conf->variable = prev->variable;
-    }
-
-    if (conf->md5 == NULL) {
-        conf->md5 = prev->md5;
-    }
+    ngx_conf_merge_ptr_value(conf->variable, prev->variable, NULL);
+    ngx_conf_merge_ptr_value(conf->md5, prev->md5, NULL);
 
     if (conf->variable == NULL && conf->md5 == NULL) {
         conf->secret = prev->secret;
diff --git a/src/http/modules/ngx_http_uwsgi_module.c b/src/http/modules/ngx_http_uwsgi_module.c
index 1334f44c9..dbcbd06d2 100644
--- a/src/http/modules/ngx_http_uwsgi_module.c
+++ b/src/http/modules/ngx_http_uwsgi_module.c
@@ -1509,6 +1509,7 @@ ngx_http_uwsgi_create_loc_conf(ngx_conf_t *cf)
 
 #if (NGX_HTTP_SSL)
     conf->upstream.ssl_session_reuse = NGX_CONF_UNSET;
+    conf->upstream.ssl_name = NGX_CONF_UNSET_PTR;
     conf->upstream.ssl_server_name = NGX_CONF_UNSET;
     conf->upstream.ssl_verify = NGX_CONF_UNSET;
     conf->ssl_verify_depth = NGX_CONF_UNSET_UINT;
@@ -1824,10 +1825,8 @@ ngx_http_uwsgi_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_str_value(conf->ssl_ciphers, prev->ssl_ciphers,
                              "DEFAULT");
 
-    if (conf->upstream.ssl_name == NULL) {
-        conf->upstream.ssl_name = prev->upstream.ssl_name;
-    }
-
+    ngx_conf_merge_ptr_value(conf->upstream.ssl_name,
+                              prev->upstream.ssl_name, NULL);
     ngx_conf_merge_value(conf->upstream.ssl_server_name,
                               prev->upstream.ssl_server_name, 0);
     ngx_conf_merge_value(conf->upstream.ssl_verify,
diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 6664fa6c3..96a945be4 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -3479,8 +3479,6 @@ ngx_http_core_create_loc_conf(ngx_conf_t *cf)
      *     clcf->exact_match = 0;
      *     clcf->auto_redirect = 0;
      *     clcf->alias = 0;
-     *     clcf->limit_rate = NULL;
-     *     clcf->limit_rate_after = NULL;
      *     clcf->gzip_proxied = 0;
      *     clcf->keepalive_disable = 0;
      */
@@ -3512,6 +3510,8 @@ ngx_http_core_create_loc_conf(ngx_conf_t *cf)
     clcf->send_timeout = NGX_CONF_UNSET_MSEC;
     clcf->send_lowat = NGX_CONF_UNSET_SIZE;
     clcf->postpone_output = NGX_CONF_UNSET_SIZE;
+    clcf->limit_rate = NGX_CONF_UNSET_PTR;
+    clcf->limit_rate_after = NGX_CONF_UNSET_PTR;
     clcf->keepalive_time = NGX_CONF_UNSET_MSEC;
     clcf->keepalive_timeout = NGX_CONF_UNSET_MSEC;
     clcf->keepalive_header = NGX_CONF_UNSET;
@@ -3743,13 +3743,9 @@ ngx_http_core_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_size_value(conf->postpone_output, prev->postpone_output,
                               1460);
 
-    if (conf->limit_rate == NULL) {
-        conf->limit_rate = prev->limit_rate;
-    }
-
-    if (conf->limit_rate_after == NULL) {
-        conf->limit_rate_after = prev->limit_rate_after;
-    }
+    ngx_conf_merge_ptr_value(conf->limit_rate, prev->limit_rate, NULL);
+    ngx_conf_merge_ptr_value(conf->limit_rate_after,
+                              prev->limit_rate_after, NULL);
 
     ngx_conf_merge_msec_value(conf->keepalive_time,
                               prev->keepalive_time, 3600000);
diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index 13c57d6d9..e94de7385 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -250,7 +250,7 @@ ngx_http_set_complex_value_slot(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
 
     cv = (ngx_http_complex_value_t **) (p + cmd->offset);
 
-    if (*cv != NULL) {
+    if (*cv != NGX_CONF_UNSET_PTR && *cv != NULL) {
         return "is duplicate";
     }
 
diff --git a/src/stream/ngx_stream_proxy_module.c b/src/stream/ngx_stream_proxy_module.c
index 01cda7a36..6f6623aa8 100644
--- a/src/stream/ngx_stream_proxy_module.c
+++ b/src/stream/ngx_stream_proxy_module.c
@@ -1977,14 +1977,11 @@ ngx_stream_proxy_create_srv_conf(ngx_conf_t *cf)
      *
      *     conf->ssl_protocols = 0;
      *     conf->ssl_ciphers = { 0, NULL };
-     *     conf->ssl_name = NULL;
      *     conf->ssl_trusted_certificate = { 0, NULL };
      *     conf->ssl_crl = { 0, NULL };
      *     conf->ssl_certificate = { 0, NULL };
      *     conf->ssl_certificate_key = { 0, NULL };
      *
-     *     conf->upload_rate = NULL;
-     *     conf->download_rate = NULL;
      *     conf->ssl = NULL;
      *     conf->upstream = NULL;
      *     conf->upstream_value = NULL;
@@ -1994,6 +1991,8 @@ ngx_stream_proxy_create_srv_conf(ngx_conf_t *cf)
     conf->timeout = NGX_CONF_UNSET_MSEC;
     conf->next_upstream_timeout = NGX_CONF_UNSET_MSEC;
     conf->buffer_size = NGX_CONF_UNSET_SIZE;
+    conf->upload_rate = NGX_CONF_UNSET_PTR;
+    conf->download_rate = NGX_CONF_UNSET_PTR;
     conf->requests = NGX_CONF_UNSET_UINT;
     conf->responses = NGX_CONF_UNSET_UINT;
     conf->next_upstream_tries = NGX_CONF_UNSET_UINT;
@@ -2005,6 +2004,7 @@ ngx_stream_proxy_create_srv_conf(ngx_conf_t *cf)
 #if (NGX_STREAM_SSL)
     conf->ssl_enable = NGX_CONF_UNSET;
     conf->ssl_session_reuse = NGX_CONF_UNSET;
+    conf->ssl_name = NGX_CONF_UNSET_PTR;
     conf->ssl_server_name = NGX_CONF_UNSET;
     conf->ssl_verify = NGX_CONF_UNSET;
     conf->ssl_verify_depth = NGX_CONF_UNSET_UINT;
@@ -2034,13 +2034,9 @@ ngx_stream_proxy_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_size_value(conf->buffer_size,
                               prev->buffer_size, 16384);
 
-    if (conf->upload_rate == NULL) {
-        conf->upload_rate = prev->upload_rate;
-    }
+    ngx_conf_merge_ptr_value(conf->upload_rate, prev->upload_rate, NULL);
 
-    if (conf->download_rate == NULL) {
-        conf->download_rate = prev->download_rate;
-    }
+    ngx_conf_merge_ptr_value(conf->download_rate, prev->download_rate, NULL);
 
     ngx_conf_merge_uint_value(conf->requests,
                               prev->requests, 0);
@@ -2073,9 +2069,7 @@ ngx_stream_proxy_merge_srv_conf(ngx_conf_t *cf, void *parent, void *child)
 
     ngx_conf_merge_str_value(conf->ssl_ciphers, prev->ssl_ciphers, "DEFAULT");
 
-    if (conf->ssl_name == NULL) {
-        conf->ssl_name = prev->ssl_name;
-    }
+    ngx_conf_merge_ptr_value(conf->ssl_name, prev->ssl_name, NULL);
 
     ngx_conf_merge_value(conf->ssl_server_name, prev->ssl_server_name, 0);
 
diff --git a/src/stream/ngx_stream_script.c b/src/stream/ngx_stream_script.c
index a15f772b5..76d347599 100644
--- a/src/stream/ngx_stream_script.c
+++ b/src/stream/ngx_stream_script.c
@@ -252,7 +252,7 @@ ngx_stream_set_complex_value_slot(ngx_conf_t *cf, ngx_command_t *cmd,
 
     cv = (ngx_stream_complex_value_t **) (p + cmd->offset);
 
-    if (*cv != NULL) {
+    if (*cv != NGX_CONF_UNSET_PTR && *cv != NULL) {
         return "is duplicate";
     }