diff --git a/tests/data_files/Readme-x509.txt b/tests/data_files/Readme-x509.txt
index 388865b..850237a 100644
--- a/tests/data_files/Readme-x509.txt
+++ b/tests/data_files/Readme-x509.txt
@@ -107,6 +107,7 @@
     _int3_int-ca2_ca.crt: S10 + I3 + I2 + 1
     _int3_spurious_int-ca2.crt: S10 + I3 + I1(spurious) + I2
  - server11.crt: 3 E, secp256r1 curve
+    -bad.crt.der: S11 with corrupted public key and signature
 
 Certificate revocation lists
 ----------------------------
diff --git a/tests/data_files/server11-bad.crt.der b/tests/data_files/server11-bad.crt.der
new file mode 100644
index 0000000..0a782a7
--- /dev/null
+++ b/tests/data_files/server11-bad.crt.der
Binary files differ