diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # hevm changelog
 
+## 0.21 - 2018-11-29
+ - Fix Hackage package by including C header files for ethjet
+
 ## 0.20 - 2018-10-27
  - Parse constructor inputs from Solidity AST
 
diff --git a/ethjet/ethjet.h b/ethjet/ethjet.h
new file mode 100644
--- /dev/null
+++ b/ethjet/ethjet.h
@@ -0,0 +1,30 @@
+#ifndef LIBETHJET_H
+#define LIBETHJET_H
+
+#include <stdint.h>
+
+#include <secp256k1.h>
+
+struct ethjet_context
+{
+  secp256k1_context *ec;
+};
+
+enum ethjet_operation
+  {
+    ETHJET_ECRECOVER = 1,
+    ETHJET_EXAMPLE = 0xdeadbeef,
+  };
+
+struct ethjet_context *
+ethjet_init ();
+
+void
+ethjet_free (struct ethjet_context *ctx);
+
+int ethjet (struct ethjet_context *ctx,
+            enum ethjet_operation op,
+            uint8_t *in, size_t in_size,
+            uint8_t *out, size_t out_size);
+
+#endif
diff --git a/ethjet/tinykeccak.h b/ethjet/tinykeccak.h
new file mode 100644
--- /dev/null
+++ b/ethjet/tinykeccak.h
@@ -0,0 +1,10 @@
+#ifndef KECCAK_H
+#define KECCAK_H
+
+#include <stdint.h>
+#include <stdlib.h>
+
+int sha3_256 (uint8_t *out, size_t out_size,
+              const uint8_t *in, size_t in_size);
+
+#endif
diff --git a/hevm.cabal b/hevm.cabal
--- a/hevm.cabal
+++ b/hevm.cabal
@@ -1,7 +1,7 @@
 name:
   hevm
 version:
-  0.20
+  0.21
 synopsis:
   Ethereum virtual machine evaluator
 description:
@@ -64,6 +64,8 @@
     secp256k1
   c-sources:
     ethjet/ethjet.c, ethjet/tinykeccak.c
+  install-includes:
+    ethjet/ethjet.h, ethjet/tinykeccak.h
   build-depends:
     QuickCheck                        >= 2.9,
     abstract-par                      >= 0.3,