diff --git a/CHANGES b/CHANGES
index 0420ab900c..02f4fdf9ef 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,6 +1,9 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.5.0
 
+  *) mod_proxy_balancer: Fix balancers and balancer members reuse on
+     restart when new ones are added.  PR 58024.  [Yann Ylavic]
+
   *) mod_socache_memcache: Add the 'MemcacheConnTTL' directive to control how 
      long to keep idle connections with the memcache server(s).
      Change default value from 600 usec (!) to 15 sec. PR 58091
diff --git a/docs/log-message-tags/next-number b/docs/log-message-tags/next-number
index ff481a2e55..ec21808e29 100644
--- a/docs/log-message-tags/next-number
+++ b/docs/log-message-tags/next-number
@@ -1 +1 @@
-2964
+2966
diff --git a/modules/proxy/mod_proxy_balancer.c b/modules/proxy/mod_proxy_balancer.c
index 5e1d78bc54..be77ef155e 100644
--- a/modules/proxy/mod_proxy_balancer.c
+++ b/modules/proxy/mod_proxy_balancer.c
@@ -761,8 +761,11 @@ static int balancer_post_config(apr_pool_t *pconf, apr_pool_t *plog,
         char *id;
         proxy_balancer *balancer;
         ap_slotmem_type_t type;
+        apr_size_t attached_size;
+        unsigned int attached_num;
         void *sconf = s->module_config;
         conf = (proxy_server_conf *)ap_get_module_config(sconf, &proxy_module);
+
         /*
          * During create_proxy_config() we created a dummy id. Now that
          * we have identifying info, we can create the real id
@@ -794,11 +797,39 @@ static int balancer_post_config(apr_pool_t *pconf, apr_pool_t *plog,
                          (int)ALIGNED_PROXY_BALANCER_SHARED_SIZE,
                          (int)conf->balancers->nelts, conf->max_balancers);
 
-            rv = storage->create(&new, conf->id,
-                                 ALIGNED_PROXY_BALANCER_SHARED_SIZE,
-                                 conf->max_balancers, type, pconf);
+            /* First try to attach() since the number of configured balancers
+             * may have changed during restart, and we don't want create() to
+             * fail because the overall size * number of entries is not stricly
+             * identical to the previous run.  There may still be enough room
+             * for this new run thanks to bgrowth margin, so if attach()
+             * succeeds we can only check for the number of available entries
+             * to be *greater or* equal to what we need now.  If attach() fails
+             * we simply fall back to create().
+             */
+            rv = storage->attach(&new, conf->id,
+                                 &attached_size, &attached_num,
+                                 pconf);
             if (rv != APR_SUCCESS) {
-                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01179) "balancer slotmem_create failed");
+                rv = storage->create(&new, conf->id,
+                                     ALIGNED_PROXY_BALANCER_SHARED_SIZE,
+                                     conf->max_balancers, type, pconf);
+            }
+            else {
+                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(02964)
+                             "Balancers attached: %d, %d (%d)",
+                             (int)ALIGNED_PROXY_BALANCER_SHARED_SIZE,
+                             (int)attached_num, conf->max_balancers);
+                if (attached_size == ALIGNED_PROXY_BALANCER_SHARED_SIZE
+                        && attached_num >= conf->balancers->nelts) {
+                    conf->max_balancers = attached_num;
+                }
+                else {
+                    rv = APR_ENOSPC;
+                }
+            }
+            if (rv != APR_SUCCESS) {
+                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01179)
+                             "balancer slotmem create or attach failed");
                 return !OK;
             }
             conf->bslot = new;
@@ -864,11 +895,32 @@ static int balancer_post_config(apr_pool_t *pconf, apr_pool_t *plog,
                          (int)ALIGNED_PROXY_WORKER_SHARED_SIZE,
                          (int)balancer->max_workers, i);
 
-            rv = storage->create(&new, balancer->s->sname,
-                                 ALIGNED_PROXY_WORKER_SHARED_SIZE,
-                                 balancer->max_workers, type, pconf);
+            /* try to attach first (see rationale from balancers above) */
+            rv = storage->attach(&new, balancer->s->sname,
+                                 &attached_size, &attached_num,
+                                 pconf);
             if (rv != APR_SUCCESS) {
-                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01185) "worker slotmem_create failed");
+                rv = storage->create(&new, balancer->s->sname,
+                                     ALIGNED_PROXY_WORKER_SHARED_SIZE,
+                                     balancer->max_workers, type, pconf);
+            }
+            else {
+                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, s, APLOGNO(02965)
+                             "Workers attached: %s (%s), %d, %d (%d) [%u]",
+                             balancer->s->name, balancer->s->sname,
+                             (int)ALIGNED_PROXY_WORKER_SHARED_SIZE,
+                             (int)attached_num, balancer->max_workers, i);
+                if (attached_size == ALIGNED_PROXY_WORKER_SHARED_SIZE
+                        && attached_num >= balancer->workers->nelts) {
+                    balancer->max_workers = attached_num;
+                }
+                else {
+                    rv = APR_ENOSPC;
+                }
+            }
+            if (rv != APR_SUCCESS) {
+                ap_log_error(APLOG_MARK, APLOG_EMERG, rv, s, APLOGNO(01185)
+                             "worker slotmem create or attach failed");
                 return !OK;
             }
             balancer->wslot = new;