diff --git a/doc/reference.conf b/doc/reference.conf
index b008d0e4..2356ac1a 100755
--- a/doc/reference.conf
+++ b/doc/reference.conf
@@ -1326,7 +1326,7 @@ general {
 	 * are not supported on servers running charybdis 3.5.3 or earlier.
 	 *
 	 * To generate a fingerprint from a certificate file, run the following:
-	 * $ openssl x509 -outform DER < your.crt | sha1sum     (or sha256sum, or sha512sum)
+	 * $ openssl x509 -outform DER -in your.crt | sha1sum     (or sha256sum, or sha512sum)
 	 *
 	 * To generate a SPKI SHA-256 fingerprint, run the following:
 	 * $ openssl x509 -pubkey -noout -in your.crt | openssl pkey -pubin -outform DER | \