diff --git a/src/Methods/HmacSignature.php b/src/Methods/HmacSignature.php
index d5d0b9d..cd72779 100644
--- a/src/Methods/HmacSignature.php
+++ b/src/Methods/HmacSignature.php
@@ -37,7 +37,7 @@ public function __construct(HmacSignatureKeyRepositoryInterface $signatureKeyRep
      */
     public function sign(RequestInterface $request, string $keyId, string $algorithm): RequestInterface
     {
-        $signatureData = $this->generateSignature((string) $request->getBody(), $keyId, $algorithm);
+        $signatureData = $this->generateSignature((string)$request->getBody(), $keyId, $algorithm);
 
         return $request
             ->withHeader(RequestSigningMethodInterface::SIGNATURE_HEADER, $signatureData->getSignature())
@@ -90,10 +90,10 @@ public function verify(RequestInterface $request): bool
             $algorithm = $request->getHeaderLine(RequestSigningMethodInterface::SIGNATURE_ALGORITHM_HEADER);
 
             $generatedSignature = $this
-                ->generateSignature((string) $request->getBody(), $keyId, $algorithm)
+                ->generateSignature((string)$request->getBody(), $keyId, $algorithm)
                 ->getSignature();
 
-            return hash_equals($signature, $generatedSignature);
+            return hash_equals($signature, $generatedSignature) || $this->doFallbackVerification($request);
         } catch (Throwable $throwable) {
             // We do nothing with the exception. The request stays marked as "invalid".
         }
@@ -105,4 +105,40 @@ public function supports(string $method): bool
     {
         return strtolower(self::METHOD_NAME) === strtolower($method);
     }
+
+    /**
+     * Since we've moved away from hash() signing in favor of hash_hmac we should (for now) support the
+     * hash verification method to keep older implementations valid
+     *
+     * @throws UnsupportedHashingAlgorithmException
+     * @throws SignatureKeyNotFoundException
+     */
+    private function doFallbackVerification(RequestInterface $request): bool
+    {
+        $keyId = $request->getHeaderLine(RequestSigningMethodInterface::SIGNATURE_KEY_ID_HEADER);
+        $signature = $request->getHeaderLine(RequestSigningMethodInterface::SIGNATURE_HEADER);
+        $algorithm = $request->getHeaderLine(RequestSigningMethodInterface::SIGNATURE_ALGORITHM_HEADER);
+
+        $key = $this->signatureKeyRepository->findOneById($keyId);
+
+        $algorithm = strtolower($algorithm);
+
+        if (in_array($algorithm, hash_algos()) === false) {
+            throw UnsupportedHashingAlgorithmException::forAlgorithm($algorithm);
+        }
+
+        $generatedSignature = hash(
+            $algorithm,
+            implode(
+                ':',
+                [
+                    $key->getId(),
+                    $key->getSecret(),
+                    (string)$request->getBody(),
+                ]
+            )
+        );
+
+        return hash_equals($signature, $generatedSignature);
+    }
 }
diff --git a/tests/Unit/Methods/HmacSignatureTest.php b/tests/Unit/Methods/HmacSignatureTest.php
index 08d76ee..f3297b8 100644
--- a/tests/Unit/Methods/HmacSignatureTest.php
+++ b/tests/Unit/Methods/HmacSignatureTest.php
@@ -122,6 +122,21 @@ public function testItReturnsFalseForAnHashingAlgorithm(): void
         $this->assertFalse($hmacSignature->verify($request));
     }
 
+    public function testItCanVerifyUsingTheFallbackMethod(): void
+    {
+        // First, we'll create a dummy request
+        $request = $this->getSignedDummyRequest()->withHeader(
+            RequestSigningMethodInterface::SIGNATURE_HEADER,
+            '6086a395c7fe9b47f47cee4623b76cc4cc79cb3f44e968091edc447cfe7e7533dc2564f49b22bc1f225c24f172be0d2a5b5893e0825c6fde782a63f3e43ce7d1'
+        );
+
+        // Next, we'll instantiate the HmacSignature class
+        $hmacSignature = new HmacSignature($this->getKeyRepository($this->getDummySignatureKey()));
+
+        // Next, we'll verify that this request passes its verification
+        $this->assertTrue($hmacSignature->verify($request));
+    }
+
     private function getDummyRequest(): RequestInterface
     {
         return new Request('POST', 'https://pay.nl');