diff --git a/tools/libs/light/libxl_x86_acpi.c b/tools/libs/light/libxl_x86_acpi.c
index 620f3c700c..5cf261bd67 100644
--- a/tools/libs/light/libxl_x86_acpi.c
+++ b/tools/libs/light/libxl_x86_acpi.c
@@ -89,7 +89,7 @@ static int init_acpi_config(libxl__gc *gc,
     uint32_t domid = dom->guest_domid;
     xc_domaininfo_t info;
     struct hvm_info_table *hvminfo;
-    int i, r, rc;
+    int r, rc;
 
     config->dsdt_anycpu = config->dsdt_15cpu = dsdt_pvh;
     config->dsdt_anycpu_len = config->dsdt_15cpu_len = dsdt_pvh_len;
@@ -138,8 +138,8 @@ static int init_acpi_config(libxl__gc *gc,
         hvminfo->nr_vcpus = info.max_vcpu_id + 1;
     }
 
-    for (i = 0; i < hvminfo->nr_vcpus; i++)
-        hvminfo->vcpu_online[i / 8] |= 1 << (i & 7);
+    memcpy(hvminfo->vcpu_online, b_info->avail_vcpus.map,
+           b_info->avail_vcpus.size);
 
     config->hvminfo = hvminfo;