diff --git a/CHANGELOG.md b/CHANGELOG.md
index 68a9120..3219399 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,11 @@
 # Change Log
 All notable changes to this project will be documented in this file. This change log follows the conventions of [keepachangelog.com](http://keepachangelog.com/).
 
+## [Unreleased]
+### Fixed
+- Long and double arguments to upcalls failed to compile in some cases
+- Void return types on upcalls would crash on serialization
+
 ## [0.1.251] - 2021-10-14
 ### Fixed
 - Bug with the inline expansion of `make-serde-wrapper`, make it more maintainable
@@ -63,6 +68,7 @@ All notable changes to this project will be documented in this file. This change
 - Support for serializing and deserializing arbitrary Clojure functions
 - Support for serializing and deserializing arbitrary Clojure data structures
 
+[Unreleased]: https://github.com/IGJoshua/coffi/compare/v0.1.251...HEAD
 [0.1.251]: https://github.com/IGJoshua/coffi/compare/v0.1.246...v0.1.251
 [0.1.246]: https://github.com/IGJoshua/coffi/compare/v0.1.241...v0.1.246
 [0.1.241]: https://github.com/IGJoshua/coffi/compare/v0.1.220...v0.1.241
diff --git a/build.clj b/build.clj
index 12135a5..039f034 100644
--- a/build.clj
+++ b/build.clj
@@ -17,7 +17,7 @@
    [clojure.tools.build.api :as b]))
 
 (def lib-coord 'org.suskalo/coffi)
-(def version (format "0.1.%s" (b/git-count-revs nil)))
+(def version (format "0.2.%s" (b/git-count-revs nil)))
 
 (def resource-dirs ["resources/"])
 
diff --git a/src/clj/coffi/ffi.clj b/src/clj/coffi/ffi.clj
index b742575..4693e0b 100644
--- a/src/clj/coffi/ffi.clj
+++ b/src/clj/coffi/ffi.clj
@@ -459,6 +459,10 @@
    ::mem/double :dreturn
    ::mem/void :return})
 
+(def ^:private double-sized?
+  "Set of primitive types which require 2 indices in the constant pool."
+  #{::mem/double ::mem/long ::mem/long-long})
+
 (defn- upcall-class
   "Constructs a class definition for a class with a single method, `upcall`, which
   boxes any primitives passed to it and calls a closed over [[IFn]]."
@@ -482,11 +486,18 @@
                           (insn-layout ret-type))
               :emit [[:aload 0]
                      [:getfield :this "upcall_ifn" IFn]
-                     (map-indexed
-                      (fn [idx arg]
-                        [[(load-instructions (mem/primitive-type arg) :aload) (inc idx)]
-                         (to-object-asm arg)])
-                      arg-types)
+                     (loop [types arg-types
+                            acc []
+                            idx 1]
+                       (if (seq types)
+                         (let [prim (mem/primitive-type (first types))]
+                           (recur (rest types)
+                                  (conj acc [[(load-instructions prim) idx]
+                                             (to-object-asm (first types))])
+                                  (cond-> (inc idx)
+                                    (double-sized? prim)
+                                    inc)))
+                         acc))
                      [:invokeinterface IFn "invoke" (repeat (inc (count arg-types)) Object)]
                      (to-prim-asm ret-type)
                      [(return-for-type ret-type :areturn)]]}]})
@@ -538,8 +549,7 @@
            (method-type arg-types ret-type)
            (function-descriptor arg-types ret-type))
           (downcall-fn arg-types ret-type)
-          (cond->
-              (not raw-fn?) (make-serde-wrapper arg-types ret-type)))
+          (cond-> (not raw-fn?) (make-serde-wrapper arg-types ret-type)))
       assoc ::address addr)))
 
 ;;; Static memory access
diff --git a/src/clj/coffi/mem.clj b/src/clj/coffi/mem.clj
index 8e87d4a..b003216 100644
--- a/src/clj/coffi/mem.clj
+++ b/src/clj/coffi/mem.clj
@@ -417,6 +417,10 @@
       obj)
     (MemoryAddress/NULL)))
 
+(defmethod serialize* ::void
+  [_obj _type _scope]
+  nil)
+
 (defmulti serialize-into
   "Writes a serialized version of the `obj` to the given `segment`.