diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index b31ccecf985..51d0915650d 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -4238,6 +4238,11 @@ public function applySpecifiedTypes(SpecifiedTypes $specifiedTypes): self
 				// a combinatorially-grown offset union doubles it with every isset()-
 				// style check and gets skipped (overwrites assign, they never narrow)
 				continue;
+			} elseif ($trackedNativeType === null) {
+				// tracked with its PHPDoc type only (e.g. by a conditional holder) -
+				// the native base is still read from the scope, not taken from
+				// the PHPDoc type
+				$trackedNativeType = $scope->getCurrentTypesOfSpecifiedExpr($expr)[1] ?? null;
 			}
 
 			if (isset($typeSpecification['terms'])) {
diff --git a/src/Turbo/TurboExtensionEnabler.php b/src/Turbo/TurboExtensionEnabler.php
index 374d29043e6..b868c5d001c 100644
--- a/src/Turbo/TurboExtensionEnabler.php
+++ b/src/Turbo/TurboExtensionEnabler.php
@@ -33,7 +33,7 @@
 final class TurboExtensionEnabler
 {
 
-	public const EXPECTED_EXTENSION_VERSION = 'a0f7086';
+	public const EXPECTED_EXTENSION_VERSION = 'f13ee08';
 
 	private static bool $active = false;
 
diff --git a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleWithUncertainPhpDocTypesTest.php b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleWithUncertainPhpDocTypesTest.php
index 635d4eff976..3f0606e1e1f 100644
--- a/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleWithUncertainPhpDocTypesTest.php
+++ b/tests/PHPStan/Rules/Comparison/ImpossibleCheckTypeFunctionCallRuleWithUncertainPhpDocTypesTest.php
@@ -272,4 +272,9 @@ public function testBug15250(): void
 		$this->analyse([__DIR__ . '/data/bug-15250.php'], []);
 	}
 
+	public function testBug15404(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-15404.php'], []);
+	}
+
 }
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-15404.php b/tests/PHPStan/Rules/Comparison/data/bug-15404.php
new file mode 100644
index 00000000000..490ad1d2896
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-15404.php
@@ -0,0 +1,17 @@
+<?php declare(strict_types = 1);
+
+namespace Bug15404;
+
+/** @param array{projects?: list<string>} $s */
+function a(array $s): void
+{
+	$has = isset($s['projects']);
+	if (!$has) {
+		return;
+	}
+	foreach ($s['projects'] as $p) {
+		if (!is_string($p)) {
+			throw new \InvalidArgumentException();
+		}
+	}
+}
diff --git a/turbo-ext/src/MutatingScope.cpp b/turbo-ext/src/MutatingScope.cpp
index 66e26133896..df008a07b10 100644
--- a/turbo-ext/src/MutatingScope.cpp
+++ b/turbo-ext/src/MutatingScope.cpp
@@ -7999,6 +7999,30 @@ class MutatingScope
 						skipSpecification = true;
 					}
 				}
+				if (!skipSpecification && !hasTrackedNative) {
+					/* tracked with its PHPDoc type only (e.g. by a conditional
+					 * holder) - the native base is still read from the scope,
+					 * not taken from the PHPDoc type */
+					zval exprZv;
+					ZVAL_OBJ(&exprZv, expr);
+					zv::Val currentTypes = otherPrivate(scopeObject, PT_LC("getcurrenttypesofspecifiedexpr"), 1, &exprZv, [&](MutatingScope &other) {
+						return other.getCurrentTypesOfSpecifiedExpr(expr);
+					});
+					if (UNEXPECTED(currentTypes.isUndef())) return zv::Val();
+					if (Z_TYPE_P(currentTypes.raw()) != IS_NULL) {
+						if (UNEXPECTED(Z_TYPE_P(currentTypes.raw()) != IS_ARRAY)) {
+							zend_throw_error(NULL, "phpstan_turbo: getCurrentTypesOfSpecifiedExpr() answered an unexpected shape");
+							return zv::Val();
+						}
+						zval *native = zend_hash_index_find(Z_ARRVAL_P(currentTypes.raw()), 1);
+						if (UNEXPECTED(native == NULL)) {
+							zend_throw_error(NULL, "phpstan_turbo: getCurrentTypesOfSpecifiedExpr() answered an unexpected shape");
+							return zv::Val();
+						}
+						trackedNativeType = zv::Val::copyOf(zv::Ref(native));
+						hasTrackedNative = true;
+					}
+				}
 			}
 			if (skipSpecification) continue;