diff --git a/phpunit/src/Build/NativeBuildConfigurationTest.php b/phpunit/src/Build/NativeBuildConfigurationTest.php
index adf730a7..e2f0d5ca 100644
--- a/phpunit/src/Build/NativeBuildConfigurationTest.php
+++ b/phpunit/src/Build/NativeBuildConfigurationTest.php
@@ -115,6 +115,25 @@ final class NativeBuildConfigurationTest extends TestCase
         }
     }
 
+    public function testAppleNanoKeepsDarwinSdkTypesVisibleUnderPosixProfile(): void
+    {
+        foreach ([new Macos(), new Ios()] as $platform) {
+            $compiler = $this->newCompiler($platform);
+            $compiler->enableNanoForTest();
+            $defines = $compiler->getCommonCompileOptionsForTest()['user_defines'];
+
+            self::assertContains('_POSIX_C_SOURCE=200809L', $defines);
+            self::assertContains('_DARWIN_C_SOURCE=1', $defines);
+        }
+
+        $compiler = $this->newCompiler(new Linux());
+        $compiler->enableNanoForTest();
+        self::assertNotContains(
+            '_DARWIN_C_SOURCE=1',
+            $compiler->getCommonCompileOptionsForTest()['user_defines'],
+        );
+    }
+
     public function testAndroidResolvesSelfContainedSdkAndSystemLibraries(): void
     {
         $phpxDir = $this->temporaryDirectory('phpx-android-host');
@@ -263,6 +282,11 @@ final class NativeBuildConfigurationTest extends TestCase
             {
                 return $this->getCommonCompileCommandOptions()->toArray();
             }
+
+            public function enableNanoForTest(): void
+            {
+                $this->nanoMode = true;
+            }
         };
 
         return $compiler->withPlatform($platform);
diff --git a/src/Build/NativeCommandOptionsTrait.php b/src/Build/NativeCommandOptionsTrait.php
index 05ffa9a6..15373b80 100644
--- a/src/Build/NativeCommandOptionsTrait.php
+++ b/src/Build/NativeCommandOptionsTrait.php
@@ -41,6 +41,12 @@ trait NativeCommandOptionsTrait
                 'PHPX_NANO=1',
                 '_POSIX_C_SOURCE=200809L',
             );
+            if ($this->isMacos() || $this->isIosTarget()) {
+                // A strict POSIX feature profile hides Darwin's BSD integer
+                // aliases (u_int/u_char/u_short), which are still used by
+                // public macOS and iOS SDK headers such as sys/sysctl.h.
+                $userDefines[] = '_DARWIN_C_SOURCE=1';
+            }
             array_push($userDefines, ...$this->nanoRuntimeDefines);
             if ($this->isWasiTarget()) {
                 $userDefines[] = 'ZEND_MM_ERROR=0';
diff --git a/src/Build/NativeSourceProjectBuilder.php b/src/Build/NativeSourceProjectBuilder.php
index ff97bd55..b65a00c8 100644
--- a/src/Build/NativeSourceProjectBuilder.php
+++ b/src/Build/NativeSourceProjectBuilder.php
@@ -111,6 +111,7 @@ final class NativeSourceProjectBuilder
                 '-DPHP_NANO=1',
                 '-DPHPX_NANO=1',
                 '-D_POSIX_C_SOURCE=200809L',
+                ...(PHP_OS_FAMILY === 'Darwin' ? ['-D_DARWIN_C_SOURCE=1'] : []),
                 ...array_map(
                     static fn(string $define): string => '-D' . $define,
                     $composition['defines'],