diff --git a/src/stage1/analyze.cpp b/src/stage1/analyze.cpp
index 5b0ea53eb4..e8958052bc 100644
--- a/src/stage1/analyze.cpp
+++ b/src/stage1/analyze.cpp
@@ -6113,7 +6113,7 @@ ZigValue *get_the_one_possible_value(CodeGen *g, ZigType *type_entry) {
         TypeUnionField *only_field = &union_type->data.unionation.fields[0];
         ZigType *field_type = resolve_union_field_type(g, only_field);
         assert(field_type);
-        bigint_init_unsigned(&result->data.x_union.tag, 0);
+        bigint_init_bigint(&result->data.x_union.tag, &only_field->enum_field->value);
         result->data.x_union.payload = g->pass1_arena->create<ZigValue>();
         copy_const_val(g, result->data.x_union.payload,
                 get_the_one_possible_value(g, field_type));