diff --git a/common/type_system/TypeSystem.cpp b/common/type_system/TypeSystem.cpp
index 82c2b2ab94..fa630da465 100644
--- a/common/type_system/TypeSystem.cpp
+++ b/common/type_system/TypeSystem.cpp
@@ -453,6 +453,27 @@ Type* TypeSystem::lookup_type_allow_partial_def(const std::string& name) const {
   return result;
 }
 
+/*!
+ * Get load size for a type.  Will succeed if one of the two conditions is true:
+ * - Is a fully defined type.
+ * - Is partially defined, but structure is in the parent.
+ * This should be safe to use to load a value from a field.
+ */
+int TypeSystem::get_load_size_allow_partial_def(const TypeSpec& ts) const {
+  auto fully_defined_it = m_types.find(ts.base_type());
+  if (fully_defined_it != m_types.end()) {
+    return fully_defined_it->second->get_load_size();
+  }
+
+  auto partial_def = lookup_type_allow_partial_def(ts);
+  if (!tc(TypeSpec("structure"), ts)) {
+    throw_typesystem_error("Cannot perform a load or store from partially defined type {}",
+                           ts.print());
+  }
+  assert(partial_def->get_load_size() == 4);
+  return partial_def->get_load_size();
+}
+
 MethodInfo TypeSystem::declare_method(const std::string& type_name,
                                       const std::string& method_name,
                                       bool no_virtual,
diff --git a/common/type_system/TypeSystem.h b/common/type_system/TypeSystem.h
index f364237737..7a3c685e83 100644
--- a/common/type_system/TypeSystem.h
+++ b/common/type_system/TypeSystem.h
@@ -154,6 +154,8 @@ class TypeSystem {
   Type* lookup_type_allow_partial_def(const TypeSpec& ts) const;
   Type* lookup_type_allow_partial_def(const std::string& name) const;
 
+  int get_load_size_allow_partial_def(const TypeSpec& ts) const;
+
   MethodInfo declare_method(const std::string& type_name,
                             const std::string& method_name,
                             bool no_virtual,
diff --git a/goalc/compiler/compilation/Define.cpp b/goalc/compiler/compilation/Define.cpp
index b8e1c838b3..c09f4748cd 100644
--- a/goalc/compiler/compilation/Define.cpp
+++ b/goalc/compiler/compilation/Define.cpp
@@ -237,17 +237,15 @@ Val* Compiler::do_set(const goos::Object& form, Val* dest, RegVal* src_in_reg, V
     // setting somewhere in memory
     auto base = as_mem_deref->base;
     auto base_as_mco = dynamic_cast<MemoryOffsetConstantVal*>(base);
+    int load_size = m_ts.get_load_size_allow_partial_def(as_mem_deref->type());
     if (base_as_mco) {
       // if it is a constant offset, we can use a fancy x86-64 addressing mode to simplify
-      auto ti = m_ts.lookup_type(as_mem_deref->type());
-      env->emit(std::make_unique<IR_StoreConstOffset>(
-          src_in_reg, base_as_mco->offset, base_as_mco->base->to_gpr(env), ti->get_load_size()));
+      env->emit(std::make_unique<IR_StoreConstOffset>(src_in_reg, base_as_mco->offset,
+                                                      base_as_mco->base->to_gpr(env), load_size));
       return src_in_reg;
     } else {
       // nope, the pointer to dereference is some complicated thing.
-      auto ti = m_ts.lookup_type(as_mem_deref->type());
-      env->emit(std::make_unique<IR_StoreConstOffset>(src_in_reg, 0, base->to_gpr(env),
-                                                      ti->get_load_size()));
+      env->emit(std::make_unique<IR_StoreConstOffset>(src_in_reg, 0, base->to_gpr(env), load_size));
       return src_in_reg;
     }
   } else if (as_pair) {
diff --git a/test/goalc/source_templates/with_game/test-partial-define-type-field.gc b/test/goalc/source_templates/with_game/test-partial-define-type-field.gc
new file mode 100644
index 0000000000..c3ee1ef6be
--- /dev/null
+++ b/test/goalc/source_templates/with_game/test-partial-define-type-field.gc
@@ -0,0 +1,10 @@
+(declare-type fake-type basic)
+(deftype type-containing-fake-type (basic)
+  ((field fake-type))
+  )
+
+(let ((obj (new 'stack 'type-containing-fake-type)))
+  (-> obj field)
+  (set! (-> obj field) (the fake-type #f))
+  (format #t "~A~%" (-> obj field))
+  )
diff --git a/test/goalc/test_with_game.cpp b/test/goalc/test_with_game.cpp
index 0cafc691c5..3db7e73a5d 100644
--- a/test/goalc/test_with_game.cpp
+++ b/test/goalc/test_with_game.cpp
@@ -545,6 +545,12 @@ TEST_F(WithGameTests, InlinedPackedBasics) {
                           "0\n"});
 }
 
+TEST_F(WithGameTests, PartialDefineTypeField) {
+  runner.run_static_test(env, testCategory, "test-partial-define-type-field.gc",
+                         {"#f\n"
+                          "0\n"});
+}
+
 // VECTOR FLOAT TESTS
 
 // ---- One off Tests