diff --git a/README.md b/README.md
index cc3beeb..b78f0ff 100644
--- a/README.md
+++ b/README.md
@@ -44,6 +44,10 @@ $location = $fileCache->get("lat-lon", $lookup);
 echo "Your location is: $location";
 ```
 
+If generating a fresh value fails, throw `Gt\FileCache\CacheValueGenerationException`
+from the callback. The cache will ignore that failure and skip writing a replacement
+value, which leaves `null` available as a legitimate cached value.
+
 # Proudly sponsored by
 
 [JetBrains Open Source sponsorship program](https://www.jetbrains.com/community/opensource/)
diff --git a/example/01-latlon.php b/example/01-latlon.php
index 3943ad3..e71e16b 100644
--- a/example/01-latlon.php
+++ b/example/01-latlon.php
@@ -17,7 +17,26 @@
 function httpJson(string $uri):object {
 	$ch = curl_init($uri);
 	curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
-	return json_decode(curl_exec($ch));
+	curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 5);
+	curl_setopt($ch, CURLOPT_TIMEOUT, 10);
+
+	$response = curl_exec($ch);
+	if($response === false) {
+		throw new Gt\FileCache\CacheValueGenerationException(curl_error($ch));
+	}
+
+	try {
+		return json_decode($response, flags: JSON_THROW_ON_ERROR);
+	}
+	catch(JsonException $exception) {
+		throw new Gt\FileCache\CacheValueGenerationException(
+			"Invalid JSON returned from $uri",
+			previous: $exception,
+		);
+	}
+	finally {
+		curl_close($ch);
+	}
 }
 
 $ipAddress = $fileCache->get("ip", function():string {
diff --git a/src/Cache.php b/src/Cache.php
index 2e07524..1986d7c 100644
--- a/src/Cache.php
+++ b/src/Cache.php
@@ -29,9 +29,14 @@ public function get(
 			return $this->fileAccess->getData($name);
 		}
 		catch(FileNotFoundException|CacheInvalidException) {
-			$value = $callback();
-			$this->fileAccess->setData($name, $value);
-			return $value;
+			try {
+				$value = $callback();
+				$this->fileAccess->setData($name, $value);
+				return $value;
+			}
+			catch(CacheValueGenerationException) {
+				return null;
+			}
 		}
 	}
 
diff --git a/test/phpunit/CacheTest.php b/test/phpunit/CacheTest.php
index 20f0e87..d6d8f75 100644
--- a/test/phpunit/CacheTest.php
+++ b/test/phpunit/CacheTest.php
@@ -2,7 +2,10 @@
 namespace Gt\FileCache\Test;
 
 use Gt\FileCache\Cache;
+use Gt\FileCache\CacheInvalidException;
+use Gt\FileCache\CacheValueGenerationException;
 use Gt\FileCache\FileAccess;
+use Gt\FileCache\FileNotFoundException;
 use PHPUnit\Framework\TestCase;
 use SplFileInfo;
 use SplFixedArray;
@@ -49,6 +52,52 @@ public function testGet_multipleCallsDoesNotCallbackMultipleTimes():void {
 		self::assertSame(1, $count);
 	}
 
+	public function testGet_nullValueCanBeCached():void {
+		$sut = $this->getSut();
+		$count = 0;
+
+		$callback = function()use(&$count):null {
+			$count++;
+			return null;
+		};
+
+		self::assertNull($sut->get("test-null", $callback));
+		self::assertNull($sut->get("test-null", $callback));
+		self::assertSame(1, $count);
+	}
+
+	public function testGet_generationExceptionDoesNotWriteInvalidValue():void {
+		$fileAccess = self::createMock(FileAccess::class);
+		$fileAccess->expects(self::once())
+			->method("checkValidity")
+			->with("test", 3600)
+			->willThrowException(new FileNotFoundException("test"));
+		$fileAccess->expects(self::never())
+			->method("setData");
+
+		$sut = new Cache(fileAccess: $fileAccess);
+
+		self::assertNull($sut->get("test", function():never {
+			throw new CacheValueGenerationException("Lookup failed");
+		}));
+	}
+
+	public function testGet_invalidCache_generationExceptionDoesNotWriteReplacement():void {
+		$fileAccess = self::createMock(FileAccess::class);
+		$fileAccess->expects(self::once())
+			->method("checkValidity")
+			->with("test", 3600)
+			->willThrowException(new CacheInvalidException("test"));
+		$fileAccess->expects(self::never())
+			->method("setData");
+
+		$sut = new Cache(fileAccess: $fileAccess);
+
+		self::assertNull($sut->get("test", function():never {
+			throw new CacheValueGenerationException("Lookup failed");
+		}));
+	}
+
 	public function testGetString():void {
 		$value = uniqid();
 		$sut = $this->getSut([