gmpy has external deps
diff --git a/tox.ini b/tox.ini
index 6ea500b..11a0821 100644
--- a/tox.ini
+++ b/tox.ini
@@ -23,10 +23,7 @@
 deps =
     # [tls,conch] syntax doesn't work here so we enumerate all dependencies.
     git+https://github.com/twisted/twisted
-    gmpy
     idna
-    pyasn1
-    pycrypto
     service_identity
 passenv = ARCHFLAGS CFLAGS LC_ALL LDFLAGS PATH LD_LIBRARY_PATH TERM
 commands =