diff --git a/NEWS b/NEWS
index 961870b6f305..1c7efd83bba0 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,10 @@ PHP                                                                        NEWS
   . Add support for CURLINFO_CONN_ID in curl_getinfo() (thecaliskan)
   . Add support for CURLINFO_QUEUE_TIME_T in curl_getinfo() (thecaliskan)
 
+- OPcache:
+  . Disallow changing opcache.memory_consumption when SHM is already set up.
+    (timwolla)
+
 - OpenSSL:
   . Add $digest_algo parameter to openssl_public_encrypt() and
     openssl_private_decrypt() functions. (Jakub Zelenka)
diff --git a/UPGRADING b/UPGRADING
index 5a206fee6d11..68b3e34390d0 100644
--- a/UPGRADING
+++ b/UPGRADING
@@ -607,6 +607,9 @@ PHP 8.5 UPGRADE NOTES
   . The default value of opcache.jit_hot_loop is now 61 (a prime) to prevent it
     from being a multiple of loop iteration counts.
     It is recommended that this parameter is set to a prime number.
+  . Changing opcache.memory_consumption when OPcache SHM is already set up
+    will now correctly report a failure instead of silently doing nothing and
+    showing misleading values in PHPInfo.
 
 - OpenSSL:
   Added openssl.libctx to select the OpenSSL library context type. Either
diff --git a/ext/opcache/ZendAccelerator.c b/ext/opcache/ZendAccelerator.c
index 0f1f1c986985..dd063c67e154 100644
--- a/ext/opcache/ZendAccelerator.c
+++ b/ext/opcache/ZendAccelerator.c
@@ -3509,6 +3509,8 @@ void accel_shutdown(void)
 	if ((ini_entry = zend_hash_str_find_ptr(EG(ini_directives), "include_path", sizeof("include_path")-1)) != NULL) {
 		ini_entry->on_modify = orig_include_path_on_modify;
 	}
+
+	accel_startup_ok = false;
 }
 
 void zend_accel_schedule_restart(zend_accel_restart_reason reason)
diff --git a/ext/opcache/zend_accelerator_module.c b/ext/opcache/zend_accelerator_module.c
index 1db7160bc889..4c103d6e061c 100644
--- a/ext/opcache/zend_accelerator_module.c
+++ b/ext/opcache/zend_accelerator_module.c
@@ -77,6 +77,15 @@ static int validate_api_restriction(void)
 
 static ZEND_INI_MH(OnUpdateMemoryConsumption)
 {
+	if (accel_startup_ok) {
+		if (strcmp(sapi_module.name, "fpm-fcgi") == 0) {
+			zend_accel_error(ACCEL_LOG_WARNING, "opcache.memory_consumption cannot be changed when OPcache is already set up. Are you using php_admin_value[opcache.memory_consumption] in an individual pool's configuration?\n");
+		} else {
+			zend_accel_error(ACCEL_LOG_WARNING, "opcache.memory_consumption cannot be changed when OPcache is already set up.\n");
+		}
+		return FAILURE;
+	}
+
 	zend_long *p = (zend_long *) ZEND_INI_GET_ADDR();
 	zend_long memsize = atoi(ZSTR_VAL(new_value));
 	/* sanity check we must use at least 8 MB */