diff --git a/mrbgems/mruby-bigint/core/bigint.c b/mrbgems/mruby-bigint/core/bigint.c
index fc43499a2..e447e0cb0 100644
--- a/mrbgems/mruby-bigint/core/bigint.c
+++ b/mrbgems/mruby-bigint/core/bigint.c
@@ -309,6 +309,15 @@ mpz_clear(mpz_ctx_t *ctx, mpz_t *s)
 static void
 mpz_move(mpz_ctx_t *ctx, mpz_t *y, mpz_t *x)
 {
+#if MRB_BIGINT_POOL_SIZE > 0
+  if (MPZ_HAS_POOL(ctx) && is_pool_memory(x, MPZ_POOL(ctx))) {
+    /* Source is pool memory - use deep copy instead of pointer transfer */
+    mpz_set(ctx, y, x);
+    mpz_clear(ctx, x);
+    return;
+  }
+#endif
+  /* Normal move: transfer ownership */
   mpz_clear(ctx, y);
   y->sn = x->sn;
   y->sz = x->sz;
@@ -2767,19 +2776,8 @@ bint_set(mpz_ctx_t *ctx, struct RBigint *b, mpz_t *x)
   }
   else {
     RBIGINT_SET_HEAP(b);
-#if MRB_BIGINT_POOL_SIZE > 0
-    if (MPZ_HAS_POOL(ctx) && is_pool_memory(x, MPZ_POOL(ctx))) {
-      /* mpz_move() cannot be used because x is in the pool. */
-      mpz_set(ctx, &b->as.heap, x);
-      mpz_clear(ctx, x);
-    }
-    else {
-#endif
-      mpz_move(ctx, &b->as.heap, x);
-    }
-#if MRB_BIGINT_POOL_SIZE > 0
+    mpz_move(ctx, &b->as.heap, x);
   }
-#endif
 }
 
 static struct RBigint*