diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index e2a6d44106..4928695393 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -454,6 +454,7 @@ libxlDomainSetVcpuAffinities(libxlDriverPrivatePtr driver, virDomainObjPtr vm)
     size_t cpumaplen;
     int vcpu;
     size_t i;
+    size_t limit;
     int ret = -1;
 
     if (libxlDoNodeGetInfo(driver, &nodeinfo) < 0)
@@ -470,7 +471,8 @@ libxlDomainSetVcpuAffinities(libxlDriverPrivatePtr driver, virDomainObjPtr vm)
 
         cpumask = (uint8_t*) def->cputune.vcpupin[vcpu]->cpumask;
 
-        for (i = 0; i < VIR_DOMAIN_CPUMASK_LEN; ++i) {
+        limit = MIN(VIR_DOMAIN_CPUMASK_LEN, cpumaplen);
+        for (i = 0; i < limit; ++i) {
             if (cpumask[i])
                 VIR_USE_CPU(cpumap, i);
         }