diff --git a/src/eval.c b/src/eval.c
index cdf3318..eac8b8c 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -27,33 +27,53 @@ apfl_ctx_destroy(apfl_ctx ctx)
     free(ctx);
 }
 
-static struct apfl_value
+static struct apfl_result
+fatal(void)
+{
+    return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+}
+
+static struct apfl_result
 evaluate_constant(struct apfl_expr_const *constant)
 {
     struct apfl_refcounted_string *rcstring;
 
     switch (constant->type) {
     case APFL_EXPR_CONST_NIL:
-        return (struct apfl_value) {
-            .type = APFL_VALUE_NIL,
+        return (struct apfl_result) {
+            .type = APFL_RESULT_OK,
+            .value = {
+                .type = APFL_VALUE_NIL,
+            },
         };
     case APFL_EXPR_CONST_BOOLEAN:
-        return (struct apfl_value) {
-            .type = APFL_VALUE_BOOLEAN,
-            .boolean = constant->boolean,
+        return (struct apfl_result) {
+            .type = APFL_RESULT_OK,
+            .value = {
+                .type = APFL_VALUE_BOOLEAN,
+                .boolean = constant->boolean,
+            },
         };
     case APFL_EXPR_CONST_STRING:
         rcstring = apfl_string_move_into_new_refcounted(&constant->string);
-        assert(rcstring != NULL); // TODO: This can fail!
+        if (rcstring == NULL) {
+            return fatal();
+        }
 
-        return (struct apfl_value) {
-            .type = APFL_VALUE_STRING,
-            .string = rcstring,
+        return (struct apfl_result) {
+            .type = APFL_RESULT_OK,
+            .value = {
+                .type = APFL_VALUE_STRING,
+                .string = rcstring,
+            },
         };
     case APFL_EXPR_CONST_NUMBER:
-        return (struct apfl_value) {
-            .type = APFL_VALUE_NUMBER,
-            .number = constant->number,
+        return (struct apfl_result) {
+            .type = APFL_RESULT_OK,
+            .value = {
+                .type = APFL_VALUE_NUMBER,
+                .number = constant->number,
+            },
         };
     }
 
@@ -83,13 +103,13 @@ evaluate_list_expr_to_list(apfl_ctx ctx, struct apfl_expr *expr, struct apfl_lis
         list->len
     )) {
         apfl_value_deinit(&result.value);
-        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+        return fatal();
     }
 
     for (size_t i = 0; i < list->len; i++) {
         if (!apfl_value_copy(&out->items[out->len], list->items[i])) {
             apfl_value_deinit(&result.value);
-            return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+            return fatal();
         }
         out->len++;
     }
@@ -124,7 +144,7 @@ evaluate_expr_list_into_list(apfl_ctx ctx, struct apfl_expr_list *list, struct a
                 1
             )) {
                 apfl_value_deinit(&result.value);
-                return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+                return fatal();
             }
         }
     }
@@ -137,7 +157,7 @@ evaluate_list(apfl_ctx ctx, struct apfl_expr_list *list)
 {
     struct apfl_list *out = apfl_list_new();
     if (out == NULL) {
-        return (struct apfl_result) { .type = APFL_RESULT_ERR_FATAL };
+        return fatal();
     }
 
     struct apfl_result result = evaluate_expr_list_into_list(ctx, list, out);
@@ -161,10 +181,7 @@ evaluate(apfl_ctx ctx, struct apfl_expr *expr)
     (void)ctx;
     switch (expr->type) {
     case APFL_EXPR_CONSTANT:
-        return (struct apfl_result) {
-            .type = APFL_RESULT_OK,
-            .value = evaluate_constant(&expr->constant),
-        };
+        return evaluate_constant(&expr->constant);
     case APFL_EXPR_LIST:
         return evaluate_list(ctx, &expr->list);
     case APFL_EXPR_VAR: