diff --git a/copilot-c99.cabal b/copilot-c99.cabal
--- a/copilot-c99.cabal
+++ b/copilot-c99.cabal
@@ -1,16 +1,16 @@
 cabal-version             : >= 1.10
 name                      : copilot-c99
-version                   : 0.2.5
+version                   : 2.1.1
 synopsis                  : A compiler for Copilot targeting C99.
-description               : 
-  This package is a back-end from Copilot to the Atom DSL. 
-  .   
+description               :
+  This package is a back-end from Copilot to the Atom DSL.
+  .
   Copilot is a stream (i.e., infinite lists) domain-specific language (DSL) in
   Haskell that compiles into embedded C.  Copilot contains an interpreter,
   multiple back-end compilers, and other verification tools.  A tutorial, bug
   reports, and todos are available at
-  <https://github.com/niswegmann/copilot-discussion>.  
-  .  
+  <https://github.com/leepike/copilot-discussion>.
+  .
   Examples are available at
   <https://github.com/leepike/Copilot/tree/master/Examples>.
 
@@ -30,7 +30,7 @@
 
 source-repository head
     type:       git
-    location:   git://github.com/niswegmann/copilot-c99.git
+    location:   git://github.com/leepike/copilot-c99.git
 
 library
   default-language        : Haskell2010
@@ -39,11 +39,11 @@
   ghc-prof-options        : -auto-all -caf-all
 
   build-depends           : atom >= 1.0.10
-                          , base >= 4.3 && < 5
+                          , base >= 4.0 && <= 5.0
                           , bytestring
                           , bytestring-csv
                           , containers >= 0.4
-                          , copilot-core
+                          , copilot-core >= 0.2.4
                           , directory >= 1.1
                           , process >= 1.0
                           , pretty >= 1.0
@@ -63,7 +63,7 @@
                           , Copilot.Compile.C99.Phases
                           , Copilot.Compile.C99.PrePostCode
                           , Copilot.Compile.C99.Queue
-                          , Copilot.Compile.C99.Witness                         
+                          , Copilot.Compile.C99.Witness
 
 executable copilot-c99-qc
   default-language        : Haskell2010
diff --git a/src/Copilot/Compile/C99/Witness.hs b/src/Copilot/Compile/C99/Witness.hs
--- a/src/Copilot/Compile/C99/Witness.hs
+++ b/src/Copilot/Compile/C99/Witness.hs
@@ -22,7 +22,8 @@
 --------------------------------------------------------------------------------
 
 badInst :: a
-badInst = C.impossible "witnesses" "copilot-c99"
+badInst = 
+  error "Fatal cast in the witnesses of Atom in copilot-sbv.  Are you sure that Atom supports the type you are using?  If you you are, or you don't understand the error, email leepike @ gmail . com (remove spaces) or file a bug report on github.com"
 
 --------------------------------------------------------------------------------