diff --git a/include/kxoptimizer.h b/include/kxoptimizer.h
index 858f46206..afa74a150 100644
--- a/include/kxoptimizer.h
+++ b/include/kxoptimizer.h
@@ -4,7 +4,7 @@
 #include <kinx.h>
 
 typedef void (*opt_ast_func_t)(kx_context_t *ctx, kx_object_t *node);
-extern void opt_ast_constant_folding(kx_context_t *ctx, kx_object_t *node);
+extern int opt_ast_constant_folding(kx_context_t *ctx, kx_object_t *node);
 
 typedef void (*opt_code_func_t)(kvec_pt(kx_code_t) *fixcode, int start);
 extern void opt_code_remove_jmp(kvec_pt(kx_code_t) *fixcode, int start);
diff --git a/src/ast_analyzer.c b/src/ast_analyzer.c
index 86725cec8..00f6bbb6b 100644
--- a/src/ast_analyzer.c
+++ b/src/ast_analyzer.c
@@ -706,36 +706,45 @@ LOOP_HEAD:;
         kx_object_t *n = NULL;
         int vtype = KX_UNKNOWN_T;
         if (!actx->lvalue && sym->optional == KXDC_CONST && sym->base->init) {
-            switch (sym->base->init->type) {
-            case KXVL_INT:
-                n = kx_gen_int_object(sym->base->init->value.i);
-                vtype = KX_INT_T;
-                break;
-            case KXVL_DBL:
-                n = kx_gen_dbl_object(sym->base->init->value.d);
-                vtype = KX_DBL_T;
-                break;
-            case KXVL_STR:
-                n = kx_gen_str_object(sym->base->init->value.s);
-                vtype = KX_CSTR_T;
-                break;
-            case KXVL_BIG:
-                n = kx_gen_big_object(sym->base->init->value.s);
-                vtype = KX_BIG_T;
-                break;
-            case KXVL_NULL:
-                n = kx_gen_special_object(KXVL_NULL);
-                vtype = KX_UND_T;
-                break;
-            case KXVL_TRUE:
-                n = kx_gen_special_object(KXVL_TRUE);
-                vtype = KX_INT_T;
-                break;
-            case KXVL_FALSE:
-                n = kx_gen_special_object(KXVL_FALSE);
-                vtype = KX_INT_T;
-                break;
-            }
+            int retry;
+            do {
+                retry = 0;
+                switch (sym->base->init->type) {
+                case KXVL_INT:
+                    n = kx_gen_int_object(sym->base->init->value.i);
+                    vtype = KX_INT_T;
+                    break;
+                case KXVL_DBL:
+                    n = kx_gen_dbl_object(sym->base->init->value.d);
+                    vtype = KX_DBL_T;
+                    break;
+                case KXVL_STR:
+                    n = kx_gen_str_object(sym->base->init->value.s);
+                    vtype = KX_CSTR_T;
+                    break;
+                case KXVL_BIG:
+                    n = kx_gen_big_object(sym->base->init->value.s);
+                    vtype = KX_BIG_T;
+                    break;
+                case KXVL_NULL:
+                    n = kx_gen_special_object(KXVL_NULL);
+                    vtype = KX_UND_T;
+                    break;
+                case KXVL_TRUE:
+                    n = kx_gen_special_object(KXVL_TRUE);
+                    vtype = KX_INT_T;
+                    break;
+                case KXVL_FALSE:
+                    n = kx_gen_special_object(KXVL_FALSE);
+                    vtype = KX_INT_T;
+                    break;
+                default:
+                    if (sym->base->init->type < KXST_EXPR) {
+                        retry = opt_ast_constant_folding(ctx, sym->base->init);
+                    }
+                    break;
+                }
+            } while (!n && retry);
             if (n) {
                 node->lhs = n;
                 analyze_ast(ctx, node->lhs, actx);    // expanding const value.
diff --git a/src/optimizer/opt_cfold.c b/src/optimizer/opt_cfold.c
index 6fd5d062e..4438a3628 100644
--- a/src/optimizer/opt_cfold.c
+++ b/src/optimizer/opt_cfold.c
@@ -1,6 +1,7 @@
 #include <kxoptimizer.h>
 
 #define KX_OPT_REPLACE_NODE(node, expr) \
+    cctx->changed++; \
     node->value.i = expr; \
     node->type = KXVL_INT; \
     node->lhs = NULL; \
@@ -9,8 +10,9 @@
 /**/
 #define KX_CONST_VAR_CHECK(p, br) { \
     kx_object_t *n = p->br; \
-    if (n->type == KXOP_VAR && n->lhs) { \
+    if (p->br != n->lhs && n->type == KXOP_VAR && n->lhs) { \
         if (n->lhs->type == KXVL_INT || n->lhs->type == KXVL_DBL) { \
+            cctx->changed++; \
             p->br = n->lhs; \
         } \
     } \
@@ -23,6 +25,7 @@ typedef struct folding_context_ {
     int exprlist_r2l;
     int in_function;
     int in_case_when;
+    int changed;
 } folding_context_t;
 
 static void opt_ast_constant_folding_impl(kx_context_t *ctx, kx_object_t *node, folding_context_t *cctx)
@@ -223,6 +226,7 @@ static void opt_ast_constant_folding_impl(kx_context_t *ctx, kx_object_t *node,
                 if (v1val % (v2val > 0 ? v2val : -v2val) == 0) {
                     KX_OPT_REPLACE_NODE(node, v1val / v2val);
                 } else {
+                    cctx->changed++;
                     node->value.d = (double)v1val / v2val;
                     node->type = KXVL_DBL;
                     node->lhs = NULL;
@@ -468,10 +472,18 @@ static void opt_ast_constant_folding_impl(kx_context_t *ctx, kx_object_t *node,
     }
 }
 
-void opt_ast_constant_folding(kx_context_t *ctx, kx_object_t *node)
+int opt_ast_constant_folding(kx_context_t *ctx, kx_object_t *node)
 {
     folding_context_t cctx = {0};
     cctx.anon_check = (node->type == KXST_STMTLIST && node->optional == 0);
     ++node->optional;
-    opt_ast_constant_folding_impl(ctx, node, &cctx);
+    int changed = 0;
+    do {
+        cctx.changed = 0;
+        opt_ast_constant_folding_impl(ctx, node, &cctx);
+        if (changed < cctx.changed) {
+            changed = cctx.changed;
+        }
+    } while (cctx.changed > 0);
+    return changed;
 }