diff --git a/Data/X509/Validation/Signature.hs b/Data/X509/Validation/Signature.hs
--- a/Data/X509/Validation/Signature.hs
+++ b/Data/X509/Validation/Signature.hs
@@ -75,4 +75,4 @@
         verifyF _ = Nothing
 
         -- TODO : need to work out how to get R/S from the bytestring
-        dsaToSignature _ = (0,0)
+        dsaToSignature _ = DSA.Signature 0 0
diff --git a/x509-validation.cabal b/x509-validation.cabal
--- a/x509-validation.cabal
+++ b/x509-validation.cabal
@@ -1,5 +1,5 @@
 Name:                x509-validation
-Version:             1.4.0
+Version:             1.4.1
 Description:         X.509 Certificate and CRL validation
 License:             BSD3
 License-file:        LICENSE
@@ -21,7 +21,8 @@
                    , asn1-types
                    , x509
                    , x509-store
-                   , crypto-pubkey
+                   , crypto-pubkey >= 0.1.4
+                   , crypto-pubkey-types >= 0.4.0
                    , cryptohash
                    , containers
                    , directory