diff --git a/phpunit/src/CompilerBaseApiTest.php b/phpunit/src/CompilerBaseApiTest.php
index 2b46ad67..5a91cdc0 100644
--- a/phpunit/src/CompilerBaseApiTest.php
+++ b/phpunit/src/CompilerBaseApiTest.php
@@ -286,7 +286,7 @@ public function testLinkedPhpRuntimeMustBeAtLeast84WithoutMatchingLanguageMinor(
     public function testMiscObjectCacheIsInvalidatedWhenCompileOptionsChange(): void
     {
         $source = $this->testDir . '/typephp_runtime.cc';
-        $object = $this->testDir . '/typephp_runtime.o';
+        $object = $this->compiler->getObjectFile($source);
         file_put_contents($source, "int typephp_runtime_test = 1;\n");
         file_put_contents($object, 'object');
         touch($source, time() - 10);
diff --git a/phpunit/src/PreprocessorTest.php b/phpunit/src/PreprocessorTest.php
index ae072fe4..3cd867b0 100644
--- a/phpunit/src/PreprocessorTest.php
+++ b/phpunit/src/PreprocessorTest.php
@@ -187,8 +187,7 @@ public function testGetObjectFile(): void
         $cppFile = $this->compiler->getBuildDir() . '/include/test.cc';
         $result = $this->compiler->getObjectFile($cppFile);
 
-        $this->assertStringEndsWith('.o', $result);
-        $this->assertStringContainsString('test', $result);
+        $this->assertSame($this->compiler->getBuildDir() . '/include/test.o', $result);
     }
 
     public function testGetObjectFileDifferentObjectExtension(): void
@@ -196,7 +195,18 @@ public function testGetObjectFileDifferentObjectExtension(): void
         // On Linux the object extension is .o
         $path = '/some/path/file.cc';
         $result = $this->compiler->getObjectFile($path);
-        $this->assertStringEndsWith('file.o', $result);
+        $this->assertStringEndsWith('file.cc.o', $result);
+    }
+
+    public function testGetObjectFileKeepsNativeSourceExtensionsDistinct(): void
+    {
+        $cObject = $this->compiler->getObjectFile('/some/path/foo.c');
+        $cppObject = $this->compiler->getObjectFile('/some/path/foo.cpp');
+        $ccObject = $this->compiler->getObjectFile('/some/path/foo.cc');
+
+        $this->assertSame('/some/path/foo.c.o', $cObject);
+        $this->assertSame('/some/path/foo.cpp.o', $cppObject);
+        $this->assertSame('/some/path/foo.cc.o', $ccObject);
     }
 
     // ========================================================================
diff --git a/src/Preprocessor.php b/src/Preprocessor.php
index 9900b40c..8bd2301d 100644
--- a/src/Preprocessor.php
+++ b/src/Preprocessor.php
@@ -340,7 +340,25 @@ public function getObjectFile(string $cppFile): string
             return $objectDir . $separator . $info['filename'] . $ext;
         }
 
-        return $info['dirname'] . $this->getPlatform()->getPathSeparator() . $info['filename'] . $ext;
+        $filename = $info['filename'];
+        if (!$this->isGeneratedCppFile($cppFile)) {
+            // Native sources keep their original paths, so their extensions
+            // distinguish files such as foo.c and foo.cpp in one directory.
+            $filename .= '.' . $info['extension'];
+        }
+
+        return $info['dirname'] . $this->getPlatform()->getPathSeparator() . $filename . $ext;
+    }
+
+    private function isGeneratedCppFile(string $file): bool
+    {
+        if (pathinfo($file, PATHINFO_EXTENSION) !== 'cc') {
+            return false;
+        }
+
+        $normalizedFile = str_replace('\\', '/', $file);
+        $normalizedBuildDir = rtrim(str_replace('\\', '/', $this->buildDir), '/') . '/';
+        return str_starts_with($normalizedFile, $normalizedBuildDir);
     }
 
     protected function isProjectRuntimeEntryFile(string $file): bool