diff --git a/src/Composer/DependencyResolver/PoolOptimizer.php b/src/Composer/DependencyResolver/PoolOptimizer.php
index 4aa6ffe324d8..841a2e9c63fe 100644
--- a/src/Composer/DependencyResolver/PoolOptimizer.php
+++ b/src/Composer/DependencyResolver/PoolOptimizer.php
@@ -420,14 +420,15 @@ private function optimizeImpossiblePackagesAway(Request $request, Pool $pool)
         foreach ($request->getLockedPackages() as $package) {
             // If this locked package is no longer required by root or anything in the pool, it may get uninstalled so do not apply its requirements
             // In a case where a requirement WERE to appear in the pool by a package that would not be used, it would've been unlocked and so not filtered still
-            $ignoreUnusedPackage = false;
+            $isUnusedPackage = true;
             foreach ($package->getNames(false) as $packageName) {
-                if (!isset($this->requireConstraintsPerPackage[$packageName])) {
-                    $ignoreUnusedPackage = true;
+                if (isset($this->requireConstraintsPerPackage[$packageName])) {
+                    $isUnusedPackage = false;
+                    break;
                 }
             }
 
-            if ($ignoreUnusedPackage) {
+            if ($isUnusedPackage) {
                 continue;
             }
 
diff --git a/tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/filter-impossible-packages-locked-replacer.test b/tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/filter-impossible-packages-locked-replacer.test
new file mode 100644
index 000000000000..cfec2e2f01c9
--- /dev/null
+++ b/tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/filter-impossible-packages-locked-replacer.test
@@ -0,0 +1,60 @@
+--TEST--
+Do not load packages into the pool that cannot meet the fixed/locked requirements, when a loose requirement is encountered during update
+(The locked replacer/pkg should restrict dependencies)
+
+--REQUEST--
+{
+    "require": {
+        "first/pkg": "*",
+        "second/pkg": "*",
+        "replacer/dep": "*"
+    },
+    "locked": [
+        {"name": "first/pkg", "version": "1.0.0", "require": {"replaced/pkg": "1.0.0"}},
+        {"name": "second/pkg", "version": "1.0.0"},
+        {"name": "replacer/pkg", "version": "1.0.0", "replace": {"replaced/pkg": "1.0.0"}, "require": {"replacer/dep": "1.*"}},
+        {"name": "replacer/dep", "version": "1.0.0"}
+    ],
+    "allowList": [
+        "second/pkg",
+        "replacer/dep"
+    ],
+    "allowTransitiveDeps": true
+}
+
+--FIXED--
+[
+]
+
+--PACKAGE-REPOS--
+[
+    [
+        {"name": "first/pkg", "version": "1.0.0", "require": {"replaced/pkg": "1.0.0"}},
+        {"name": "first/pkg", "version": "1.1.0", "require": {"replaced/pkg": "2.0.0"}},
+        {"name": "second/pkg", "version": "1.0.0"},
+        {"name": "replacer/pkg", "version": "1.0.0", "replace": {"replaced/pkg": "1.0.0"}, "require": {"replacer/dep": "1.*"}},
+        {"name": "replacer/pkg", "version": "1.1.0", "replace": {"replaced/pkg": "2.0.0"}, "require": {"replacer/dep": "1.*"}},
+        {"name": "replacer/pkg", "version": "1.2.0", "replace": {"replaced/pkg": "3.0.0"}, "require": {"replacer/dep": "1.*"}},
+        {"name": "replacer/dep", "version": "1.0.0"},
+        {"name": "replacer/dep", "version": "1.0.1"},
+        {"name": "replacer/dep", "version": "2.0.0"}
+    ]
+]
+
+--EXPECT--
+[
+    "first/pkg-1.0.0.0 (locked)",
+    "replacer/pkg-1.0.0.0 (locked)",
+    "second/pkg-1.0.0.0",
+    "replacer/dep-1.0.0.0",
+    "replacer/dep-1.0.1.0",
+    "replacer/dep-2.0.0.0"
+]
+
+--EXPECT-OPTIMIZED--
+[
+    "first/pkg-1.0.0.0 (locked)",
+    "replacer/pkg-1.0.0.0 (locked)",
+    "second/pkg-1.0.0.0",
+    "replacer/dep-1.0.1.0"
+]