diff --git a/lib/BuiltinParamNames.php b/lib/BuiltinParamNames.php
index 45f523e5b10..8234ec85afb 100644
--- a/lib/BuiltinParamNames.php
+++ b/lib/BuiltinParamNames.php
@@ -202,6 +202,9 @@ public static function forFunction(string $name): ?array
                 return ['iterator', 'preserve_keys'];
             case 'hrtime':
                 return ['as_number'];
+            case 'memory_get_usage':
+            case 'memory_get_peak_usage':
+                return ['real_usage'];
             case 'microtime':
                 return ['as_float'];
             case 'trim':
diff --git a/test/repro/maintainer_gap_memory_get_usage_named_real_usage.php b/test/repro/maintainer_gap_memory_get_usage_named_real_usage.php
new file mode 100644
index 00000000000..207ba7c262e
--- /dev/null
+++ b/test/repro/maintainer_gap_memory_get_usage_named_real_usage.php
@@ -0,0 +1,8 @@
+<?php
+
+declare(strict_types=1);
+
+$usage = memory_get_usage(real_usage: true);
+$peak = memory_get_peak_usage(real_usage: true);
+echo 'memory_get_usage_named_ok=', is_int($usage) && $usage > 0 ? '1' : '0', "\n";
+echo 'memory_get_peak_usage_named_ok=', is_int($peak) && $peak > 0 ? '1' : '0', "\n";
diff --git a/test/unit/BuiltinParamNamesAliasTest.php b/test/unit/BuiltinParamNamesAliasTest.php
index 0170000c7f0..75ffa9fe9e3 100644
--- a/test/unit/BuiltinParamNamesAliasTest.php
+++ b/test/unit/BuiltinParamNamesAliasTest.php
@@ -112,6 +112,16 @@ public function testMicrotimeAsFloatNamedParamResolves(): void
         self::assertSame(0, BuiltinParamNames::lookupNamedParamIndex($names, 'as_float', 'microtime'));
     }
 
+    /** @covers issue #11578 */
+    public function testMemoryGetUsageNamedRealUsageParamResolves(): void
+    {
+        foreach (['memory_get_usage', 'memory_get_peak_usage'] as $fn) {
+            $names = BuiltinParamNames::forFunction($fn);
+            self::assertSame(['real_usage'], $names, $fn);
+            self::assertSame(0, BuiltinParamNames::lookupNamedParamIndex($names, 'real_usage', $fn));
+        }
+    }
+
     /** @covers issue #10027 */
     public function testTrimCharactersNamedParamResolves(): void
     {