diff --git a/src/http/modules/ngx_http_not_modified_filter_module.c b/src/http/modules/ngx_http_not_modified_filter_module.c
index 032ba96fd..8cddecc25 100644
--- a/src/http/modules/ngx_http_not_modified_filter_module.c
+++ b/src/http/modules/ngx_http_not_modified_filter_module.c
@@ -54,6 +54,8 @@ static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
 static ngx_int_t
 ngx_http_not_modified_header_filter(ngx_http_request_t *r)
 {
+    ngx_http_core_loc_conf_t  *clcf;
+
     if (r->headers_out.status != NGX_HTTP_OK
         || r != r->main
         || r->disable_not_modified)
@@ -77,19 +79,58 @@ ngx_http_not_modified_header_filter(ngx_http_request_t *r)
 
     if (r->headers_in.if_modified_since || r->headers_in.if_none_match) {
 
-        if (r->headers_in.if_modified_since
-            && ngx_http_test_if_modified(r))
-        {
+        clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
+
+        if (clcf->not_modified_check == NGX_HTTP_NMC_STRICT) {
+            if (r->headers_in.if_modified_since
+                && ngx_http_test_if_modified(r))
+            {
+                return ngx_http_next_header_filter(r);
+            }
+
+            if (r->headers_in.if_none_match
+                && !ngx_http_test_if_match(r, r->headers_in.if_none_match, 1))
+            {
+                return ngx_http_next_header_filter(r);
+            }
+
+        } else if (clcf->not_modified_check == NGX_HTTP_NMC_PREFER_INM) {
+            if (r->headers_in.if_none_match) {
+                if (ngx_http_test_if_match(r, r->headers_in.if_none_match, 1))
+                {
+                    goto not_modified;
+                }
+
+                return ngx_http_next_header_filter(r);
+            }
+
+            if (r->headers_in.if_modified_since
+                && ngx_http_test_if_modified(r))
+            {
+                return ngx_http_next_header_filter(r);
+            }
+
+        } else if (clcf->not_modified_check == NGX_HTTP_NMC_ANY) {
+
+            if (r->headers_in.if_modified_since
+                && !ngx_http_test_if_modified(r))
+            {
+                goto not_modified;
+            }
+
+            if (r->headers_in.if_none_match
+                && ngx_http_test_if_match(r, r->headers_in.if_none_match, 1))
+            {
+                goto not_modified;
+            }
+
+            return ngx_http_next_header_filter(r);
+
+        } else { /* NGX_HTTP_NMC_OFF */
             return ngx_http_next_header_filter(r);
         }
 
-        if (r->headers_in.if_none_match
-            && !ngx_http_test_if_match(r, r->headers_in.if_none_match, 1))
-        {
-            return ngx_http_next_header_filter(r);
-        }
-
-        /* not modified */
+not_modified:
 
         r->headers_out.status = NGX_HTTP_NOT_MODIFIED;
         r->headers_out.status_line.len = 0;
diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 92c3eae8a..f94f24775 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -129,6 +129,15 @@ static ngx_conf_enum_t  ngx_http_core_server_tokens[] = {
 };
 
 
+static ngx_conf_enum_t  ngx_http_core_not_modified_check[] = {
+    { ngx_string("off"), NGX_HTTP_NMC_OFF },
+    { ngx_string("any"), NGX_HTTP_NMC_ANY },
+    { ngx_string("strict"), NGX_HTTP_NMC_STRICT },
+    { ngx_string("prefer_if_none_match"), NGX_HTTP_NMC_PREFER_INM },
+    { ngx_null_string, 0 }
+};
+
+
 static ngx_conf_enum_t  ngx_http_core_if_modified_since[] = {
     { ngx_string("off"), NGX_HTTP_IMS_OFF },
     { ngx_string("exact"), NGX_HTTP_IMS_EXACT },
@@ -642,6 +651,13 @@ static ngx_command_t  ngx_http_core_commands[] = {
       offsetof(ngx_http_core_loc_conf_t, server_tokens),
       &ngx_http_core_server_tokens },
 
+    { ngx_string("not_modified_check"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_enum_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_core_loc_conf_t, not_modified_check),
+      &ngx_http_core_not_modified_check },
+
     { ngx_string("if_modified_since"),
       NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
       ngx_conf_set_enum_slot,
@@ -3592,6 +3608,7 @@ ngx_http_core_create_loc_conf(ngx_conf_t *cf)
     clcf->client_body_timeout = NGX_CONF_UNSET_MSEC;
     clcf->satisfy = NGX_CONF_UNSET_UINT;
     clcf->auth_delay = NGX_CONF_UNSET_MSEC;
+    clcf->not_modified_check = NGX_CONF_UNSET_UINT;
     clcf->if_modified_since = NGX_CONF_UNSET_UINT;
     clcf->max_ranges = NGX_CONF_UNSET_UINT;
     clcf->client_body_in_file_only = NGX_CONF_UNSET_UINT;
@@ -3812,6 +3829,8 @@ ngx_http_core_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
     ngx_conf_merge_uint_value(conf->satisfy, prev->satisfy,
                               NGX_HTTP_SATISFY_ALL);
     ngx_conf_merge_msec_value(conf->auth_delay, prev->auth_delay, 0);
+    ngx_conf_merge_uint_value(conf->not_modified_check,
+                              prev->not_modified_check, NGX_HTTP_NMC_STRICT);
     ngx_conf_merge_uint_value(conf->if_modified_since, prev->if_modified_since,
                               NGX_HTTP_IMS_EXACT);
     ngx_conf_merge_uint_value(conf->max_ranges, prev->max_ranges,
diff --git a/src/http/ngx_http_core_module.h b/src/http/ngx_http_core_module.h
index e7e266bf8..7d225cc17 100644
--- a/src/http/ngx_http_core_module.h
+++ b/src/http/ngx_http_core_module.h
@@ -60,6 +60,12 @@ typedef struct ngx_thread_pool_s  ngx_thread_pool_t;
 #define NGX_HTTP_SERVER_TOKENS_BUILD    2
 
 
+#define NGX_HTTP_NMC_OFF                0
+#define NGX_HTTP_NMC_ANY                1
+#define NGX_HTTP_NMC_STRICT             2
+#define NGX_HTTP_NMC_PREFER_INM         3
+
+
 typedef struct ngx_http_location_tree_node_s  ngx_http_location_tree_node_t;
 typedef struct ngx_http_core_loc_conf_s  ngx_http_core_loc_conf_t;
 
@@ -384,6 +390,7 @@ struct ngx_http_core_loc_conf_s {
     ngx_uint_t    keepalive_disable;       /* keepalive_disable */
     ngx_uint_t    satisfy;                 /* satisfy */
     ngx_uint_t    lingering_close;         /* lingering_close */
+    ngx_uint_t    not_modified_check;      /* not_modified_check */
     ngx_uint_t    if_modified_since;       /* if_modified_since */
     ngx_uint_t    max_ranges;              /* max_ranges */
     ngx_uint_t    client_body_in_file_only; /* client_body_in_file_only */