diff --git a/kvm-all.c b/kvm-all.c
index 9f18ea38b9..7e05f08c2e 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -965,7 +965,7 @@ void kvm_init_irq_routing(KVMState *s)
 {
     int gsi_count, i;
 
-    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING);
+    gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1;
     if (gsi_count > 0) {
         unsigned int gsi_bits, i;