diff --git a/README.md b/README.md
index e9901a5..a0ebd95 100644
--- a/README.md
+++ b/README.md
@@ -12,8 +12,7 @@ Requirements
 ------------
 
   * Python (2.7+ and 3.5+ should work)
-  * cryptography
-  * six (already a dependency of cryptography, for compatibility with Python 2.7)
+  * cryptography (includes the required six and optional idna module)
 
 Optional packages (required to use specified features)
 ------------------------------------------------------
@@ -21,6 +20,7 @@ Optional packages (required to use specified features)
   * PyYAML: to parse YAML-formatted configuration files
   * dnspython: used by dns.* challenge handlers
   * idna: to allow automatic conversion of unicode domain names to their IDNA2008 counterparts
+  * cryptography>=2.1: for creating certificates with the OCSP must-staple flag (cert_must_staple)
 
 Setup
 -----
diff --git a/docs/archlinux/python-acertmgr/PKGBUILD b/docs/archlinux/python-acertmgr/PKGBUILD
index 572bf81..578c42c 100644
--- a/docs/archlinux/python-acertmgr/PKGBUILD
+++ b/docs/archlinux/python-acertmgr/PKGBUILD
@@ -7,9 +7,11 @@ arch=('any')
 url='https://github.com/moepman/acertmgr'
 license=('ISC')
 depends=('python-cryptography')
-optdepends=('yaml: python-yaml'
-            'idna: python-idna'
-	        'dns.nsupdate: python-dnspython')
+optdepends=('python-yaml: Support config files in YAML format'
+            'python-idna: Support conversion of unicode domains'
+	    'python-dnspython: Support for dns challenge handlers'
+	    'python-cryptography>=2.1: Support for the OCSP must-staple flag'
+	   )
 makedepends=('git')
 conflicts=('python-acertmgr')
 provides=('python-acertmgr')
diff --git a/docs/archlinux/python2-acertmgr/PKGBUILD b/docs/archlinux/python2-acertmgr/PKGBUILD
index a56e77c..79e5a7f 100644
--- a/docs/archlinux/python2-acertmgr/PKGBUILD
+++ b/docs/archlinux/python2-acertmgr/PKGBUILD
@@ -7,9 +7,11 @@ arch=('any')
 url='https://github.com/moepman/acertmgr'
 license=('ISC')
 depends=('python2-cryptography')
-optdepends=('yaml: python2-yaml'
-            'idna: python2-idna'
-	        'dns.nsupdate: python2-dnspython')
+optdepends=('python2-yaml: Support config files in YAML format'
+            'python2-idna: Support conversion of unicode domains'
+	    'python2-dnspython: Support for dns challenge handlers'
+	    'python2-cryptography>=2.1: Support for the OCSP must-staple flag'
+	   )
 makedepends=('git')
 conflicts=('python-acertmgr')
 provides=('python-acertmgr')
@@ -29,4 +31,4 @@ build() {
 package() {
   cd $_pkgname
   python2 setup.py install --root=${pkgdir} --optimize=1
-}
\ No newline at end of file
+}
diff --git a/setup.py b/setup.py
index 22997ce..8a42319 100644
--- a/setup.py
+++ b/setup.py
@@ -69,7 +69,7 @@ setup(
         "six",
     ],
     extras_require={
-        "dns.nsupdate": [
+        "dns": [
             "dnspython",
         ],
         "yaml": [
@@ -78,6 +78,9 @@ setup(
         "idna": [
             "idna",
         ],
+        "ocsp-must-staple": [
+            "cryptography>=2.1",
+        ],
     },
     entry_points={
         'console_scripts': [