diff --git a/c/jit.c b/c/jit.c
index 1525127..1a25708 100644
--- a/c/jit.c
+++ b/c/jit.c
@@ -839,6 +839,18 @@ static bool emit_expr(JitCtx *j, Value expr, bool tail) {
             int saved_loop_start = j->loop_start;
             int saved_loop_nparams = j->loop_nparams;
             Value *saved_loop_params = j->loop_params;
+            /* 2026-06-14: loop_slots is an ARRAY (memcpy'd in below); save it
+             * for nested named-let restore. Without this, inner (let loop ...)
+             * overwrites outer's slots and outer recursive call writes args to
+             * inner's slots → outer's bindings appear stale → "set! undefined"
+             * or wrong values at recursion. Bug surfaced in squaring.lsp's
+             * round84-fold-hi-into-lo-aggregate with outer terms-keyed loop +
+             * 4 inner (let loop ((i 0))). */
+            int saved_loop_slots[MAX_JIT_LOCALS];
+            if (saved_loop_nparams > 0 && saved_loop_nparams <= MAX_JIT_LOCALS) {
+                memcpy(saved_loop_slots, j->loop_slots,
+                       sizeof(int) * saved_loop_nparams);
+            }
 
             /* Pre-compute stack slots (but don't register yet — inits use outer scope) */
             Value loop_var_syms[MAX_JIT_LOCALS];
@@ -899,6 +911,10 @@ static bool emit_expr(JitCtx *j, Value expr, bool tail) {
             j->loop_start = saved_loop_start;
             j->loop_nparams = saved_loop_nparams;
             j->loop_params = saved_loop_params;
+            if (saved_loop_nparams > 0 && saved_loop_nparams <= MAX_JIT_LOCALS) {
+                memcpy(j->loop_slots, saved_loop_slots,
+                       sizeof(int) * saved_loop_nparams);
+            }
             return true;
         }