diff --git a/self_hosted/create_llvm_ir.jou b/self_hosted/create_llvm_ir.jou
index 21ccdc2b..ea9349c4 100644
--- a/self_hosted/create_llvm_ir.jou
+++ b/self_hosted/create_llvm_ir.jou
@@ -85,9 +85,12 @@ def class_type_to_llvm(fields: ClassField*, nfields: int) -> LLVMType*:
         end = start + 1
         while end < nfields and fields[start].union_id == fields[end].union_id:
             end++
+        assert fields[start].union_id == combined_len
         elem_types[combined_len++] = create_llvm_union_type(&elem_types[start], end-start)
 
     result = LLVMStructType(elem_types, combined_len, False as int)
+    for i = 0; i < combined_len; i++:
+        assert LLVMStructGetTypeAtIndex(result, i) == elem_types[i]
     free(elem_types)
     return result
 
@@ -234,7 +237,7 @@ class AstToIR:
         p1 = LLVMBuildAlloca(self->builder, LLVMTypeOf(value), "cast_through_ptr_temp")
         LLVMBuildStore(self->builder, value, p1)
         p2 = LLVMBuildBitCast(self->builder, p1, LLVMPointerType(to, 0), "cast_through_ptr_temp")
-        return LLVMBuildLoad(self->builder, p2, "cast_through_ptr_result")
+        return LLVMBuildLoad2(self->builder, to, p2, "cast_through_ptr_result")
 
     def do_binop(
         self,
@@ -584,6 +587,7 @@ class AstToIR:
                 value = self->do_expression(&ast->instantiation.field_values[i])
                 if field_uses_i8_ptr_hack(field) or field->belongs_to_union:
                     value = self->do_cast_through_pointers(value, LLVMStructGetTypeAtIndex(type_to_llvm(instance_type), field->union_id))
+                    assert LLVMTypeOf(value) == LLVMStructGetTypeAtIndex(type_to_llvm(instance_type), field->union_id)
                 result = LLVMBuildInsertValue(self->builder, result, value, field->union_id, "instance")
 
         elif ast->kind == AstExpressionKind::GetClassField:
diff --git a/self_hosted/llvm.jou b/self_hosted/llvm.jou
index c4423e61..abd7b1ee 100644
--- a/self_hosted/llvm.jou
+++ b/self_hosted/llvm.jou
@@ -215,6 +215,7 @@ declare LLVMGetParam(Fn: LLVMValue*, Index: int) -> LLVMValue*
 declare LLVMGetElementType(Ty: LLVMType*) -> LLVMType*
 declare LLVMStructGetTypeAtIndex(StructTy: LLVMType*, i: int) -> LLVMType*
 declare LLVMTypeOf(Val: LLVMValue*) -> LLVMType*
+declare LLVMAlignOf(Ty: LLVMType*) -> LLVMValue*
 declare LLVMConstNull(Ty: LLVMType*) -> LLVMValue*
 declare LLVMGetUndef(Ty: LLVMType*) -> LLVMValue*
 declare LLVMConstInt(IntTy: LLVMType*, N: long, SignExtend: int) -> LLVMValue*
@@ -252,8 +253,10 @@ declare LLVMBuildXor(Builder: LLVMBuilder*, LHS: LLVMValue*, RHS: LLVMValue*, Na
 declare LLVMBuildNeg(Builder: LLVMBuilder*, V: LLVMValue*, Name: byte*) -> LLVMValue*
 declare LLVMBuildFNeg(Builder: LLVMBuilder*, V: LLVMValue*, Name: byte*) -> LLVMValue*
 declare LLVMBuildMemSet(Builder: LLVMBuilder*, Ptr: LLVMValue*, Val: LLVMValue*, Len: LLVMValue*, Align: int) -> LLVMValue*
+declare LLVMBuildMemCpy(Builder: LLVMBuilder*, Dst: LLVMValue*, DstAlign: int, Src: LLVMValue*, SrcAlign: int, Size: LLVMValue*) -> LLVMValue*
 declare LLVMBuildAlloca(Builder: LLVMBuilder*, Ty: LLVMType*, Name: byte*) -> LLVMValue*
 declare LLVMBuildLoad(Builder: LLVMBuilder*, PointerVal: LLVMValue*, Name: byte*) -> LLVMValue*
+declare LLVMBuildLoad2(Builder: LLVMBuilder*, Ty: LLVMType*, PointerVal: LLVMValue*, Name: byte*) -> LLVMValue*
 declare LLVMBuildStore(Builder: LLVMBuilder*, Val: LLVMValue*, Ptr: LLVMValue*) -> LLVMValue*
 declare LLVMBuildGEP(Builder: LLVMBuilder*, Pointer: LLVMValue*, Indices: LLVMValue**, NumIndices: int, Name: byte*) -> LLVMValue*
 declare LLVMBuildStructGEP2(Builder: LLVMBuilder*, Ty: LLVMType*, Pointer: LLVMValue*, Idx: int, Name: byte*) -> LLVMValue*