diff --git a/src/core/ngx_conf_file.c b/src/core/ngx_conf_file.c
index 6d1629e..fec7bb8 100644
--- a/src/core/ngx_conf_file.c
+++ b/src/core/ngx_conf_file.c
@@ -1137,7 +1137,7 @@
 
     a = (ngx_array_t **) (p + cmd->offset);
 
-    if (*a == NULL) {
+    if (*a == NGX_CONF_UNSET_PTR || *a == NULL) {
         *a = ngx_array_create(cf->pool, 4, sizeof(ngx_keyval_t));
         if (*a == NULL) {
             return NGX_CONF_ERROR;
diff --git a/src/http/modules/ngx_http_grpc_module.c b/src/http/modules/ngx_http_grpc_module.c
index ab4ad6b..d5e84a7 100644
--- a/src/http/modules/ngx_http_grpc_module.c
+++ b/src/http/modules/ngx_http_grpc_module.c
@@ -4324,7 +4324,6 @@
      *     conf->upstream.hide_headers_hash = { NULL, 0 };
      *     conf->upstream.ssl_name = NULL;
      *
-     *     conf->headers_source = NULL;
      *     conf->headers.lengths = NULL;
      *     conf->headers.values = NULL;
      *     conf->headers.hash = { NULL, 0 };
@@ -4377,6 +4376,8 @@
     conf->upstream.pass_trailers = 1;
     conf->upstream.preserve_output = 1;
 
+    conf->headers_source = NGX_CONF_UNSET_PTR;
+
     ngx_str_set(&conf->upstream.module, "grpc");
 
     return conf;
@@ -4507,9 +4508,10 @@
         clcf->handler = ngx_http_grpc_handler;
     }
 
-    if (conf->headers_source == NULL) {
+    ngx_conf_merge_ptr_value(conf->headers_source, prev->headers_source, NULL);
+
+    if (conf->headers_source == prev->headers_source) {
         conf->headers = prev->headers;
-        conf->headers_source = prev->headers_source;
         conf->host_set = prev->host_set;
     }
 
diff --git a/src/http/modules/ngx_http_proxy_module.c b/src/http/modules/ngx_http_proxy_module.c
index c5c9e85..413aec9 100644
--- a/src/http/modules/ngx_http_proxy_module.c
+++ b/src/http/modules/ngx_http_proxy_module.c
@@ -3268,7 +3268,6 @@
      *     conf->method = NULL;
      *     conf->location = NULL;
      *     conf->url = { 0, NULL };
-     *     conf->headers_source = NULL;
      *     conf->headers.lengths = NULL;
      *     conf->headers.values = NULL;
      *     conf->headers.hash = { NULL, 0 };
@@ -3346,6 +3345,8 @@
     /* "proxy_cyclic_temp_file" is disabled */
     conf->upstream.cyclic_temp_file = 0;
 
+    conf->headers_source = NGX_CONF_UNSET_PTR;
+
     conf->redirect = NGX_CONF_UNSET;
     conf->upstream.change_buffering = 1;
 
@@ -3819,12 +3820,13 @@
         }
     }
 
-    if (conf->headers_source == NULL) {
+    ngx_conf_merge_ptr_value(conf->headers_source, prev->headers_source, NULL);
+
+    if (conf->headers_source == prev->headers_source) {
         conf->headers = prev->headers;
 #if (NGX_HTTP_CACHE)
         conf->headers_cache = prev->headers_cache;
 #endif
-        conf->headers_source = prev->headers_source;
     }
 
     rc = ngx_http_proxy_init_headers(cf, conf, &conf->headers,