diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0e6c2f..24d3311 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ All notable changes to this project will be documented in this file. This change
 ### Fixed
 - Long and double arguments to upcalls failed to compile in some cases
 - Void return types on upcalls would crash on serialization
+- Non-primitive types on upcalls was unsupported and would generate invalid bytecode with `nil` instructions
 
 ## [0.1.251] - 2021-10-14
 ### Fixed
diff --git a/src/clj/coffi/ffi.clj b/src/clj/coffi/ffi.clj
index 87fe7c2..3862ce4 100644
--- a/src/clj/coffi/ffi.clj
+++ b/src/clj/coffi/ffi.clj
@@ -490,7 +490,7 @@
                        (if (seq types)
                          (let [prim (mem/primitive-type (first types))]
                            (recur (rest types)
-                                  (conj acc [[(load-instructions prim) idx]
+                                  (conj acc [[(load-instructions prim :aload) idx]
                                              (to-object-asm (first types))])
                                   (cond-> (inc idx)
                                     (double-sized? prim)