diff --git a/NgxExport/Tools/Prometheus.hs b/NgxExport/Tools/Prometheus.hs
--- a/NgxExport/Tools/Prometheus.hs
+++ b/NgxExport/Tools/Prometheus.hs
@@ -226,8 +226,8 @@
 --         location \/ {
 --             haskell_run __/toPrometheusMetrics/__ $hs_prom_metrics
 --                     '[\"__/main/__\"
---                      ,__/$cnt_collection/__
---                      ,__/$cnt_histograms/__
+--                      ,$__/cnt_collection/__
+--                      ,$__/cnt_histograms/__
 --                      ,{\"cnt_stub_status_active\": $cnt_stub_status_active
 --                       ,\"cnt_uptime\": $cnt_uptime
 --                       ,\"cnt_uptime_reload\": $cnt_uptime_reload
@@ -620,8 +620,17 @@
 --         histogram $__/hst_u_response_time/__ 11 $u_response_time_bucket;
 --         haskell_run scale1000 $hs_u_response_time_scaled $hs_u_response_time;
 --         counter $__/hst_u_response_time_sum/__ inc $hs_u_response_time_scaled;
+--
+--         counter $__/hst_u_response_time_00/__ undo;
+--         counter $__/hst_u_response_time_cnt/__ undo;
 -- @
 --
+-- Notice that the first bucket /hst_u_response_time_00/ and the total count
+-- value /hst_u_response_time_cnt/ of histogram /hst_u_response_time/ were
+-- temporarily disabled to not count visiting unrelated locations (i.e. /\//,
+-- /\/1/, and /\/404/): the two counters will be later re-enabled in locations
+-- related to proxying requests.
+--
 -- So many new variables require a bigger hash table to store them.
 --
 -- @
@@ -629,7 +638,7 @@
 -- @
 --
 -- And finally, we have to update counters declarations in
--- /simpleService_prometheusConf/ and add  location /\/backends/ in the main
+-- /simpleService_prometheusConf/ and add location /\/backends/ in the main
 -- server.
 --
 -- @
@@ -657,19 +666,24 @@
 -- @
 -- @
 --         location \/backends {
+--             counter $__/hst_u_response_time_00/__ inc $inc_hst_u_response_time_00;
+--             counter $__/hst_u_response_time_cnt/__ inc $inc_hst_u_response_time_cnt;
 --             error_page 404 \@status404;
 --             proxy_intercept_errors on;
 --             proxy_pass http:\/\/backends;
 --         }
 --
 --         location \@status404 {
+--             counter $__/hst_u_response_time_00/__ inc $inc_hst_u_response_time_00;
+--             counter $__/hst_u_response_time_cnt/__ inc $inc_hst_u_response_time_cnt;
 --             echo_sleep 0.2;
 --             echo \"Caught 404\";
 --         }
 -- @
 --
 -- We are going to additionally increase response time by /0.2/ seconds when a
--- backend server responds with HTTP status /404/.
+-- backend server responds with HTTP status /404/, and this is why location
+-- /\@status404/ was added.
 --
 -- ==== A simple test
 --
@@ -754,21 +768,7 @@
 -- and 9), the sum of cumulative response times from backends is approximately 5
 -- seconds, while the sum of all requests durations is approximately 7 seconds
 -- which corresponds to 11 visits to location /\@status404/ and the sleep time
--- /0.2/ seconds that was added there. Notice that upstream response times will
--- be updated on entering /any/ location in the main server as the histogram and
--- its sum counter were declared on the server level. To update the histogram on
--- entering location /\/backends/ only, it is possible to move the declarations
--- inside this location, however in this case there will be no updates in
--- location /\@status404/ as there is no way to declare the same histogram more
--- than once in a single counter set. Another solution would be putting line
---
--- @
---             set $u_response_time_bucket unavailable;
--- @
---
--- into all other locations of the main server (i.e. /\//, /\/1/, and /\/404/):
--- in this case only counter /hst_u_response_time_err/ will be updated when
--- entering these locations.
+-- /0.2/ seconds that was added there.
 
 extractValues :: ByteString -> [ByteString]
 extractValues = filter ((&&) <$> not . C8.null <*> isDigit . C8.head)
diff --git a/ngx-export-tools-extra.cabal b/ngx-export-tools-extra.cabal
--- a/ngx-export-tools-extra.cabal
+++ b/ngx-export-tools-extra.cabal
@@ -1,5 +1,5 @@
 name:                       ngx-export-tools-extra
-version:                    0.5.2.0
+version:                    0.5.2.1
 synopsis:                   More extra tools for Nginx haskell module
 description:                More extra tools for
         <https://github.com/lyokha/nginx-haskell-module Nginx haskell module>.