diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
index d6491df8e7..ec709e5f47 100644
--- a/xen/arch/x86/hvm/ioreq.c
+++ b/xen/arch/x86/hvm/ioreq.c
@@ -47,7 +47,7 @@ bool arch_vcpu_ioreq_completion(enum vio_completion completion)
 
     default:
         ASSERT_UNREACHABLE();
-        break;
+        return false;
     }
 
     return true;
diff --git a/xen/include/xen/ioreq.h b/xen/include/xen/ioreq.h
index 4f3c6b598d..e86f0869fa 100644
--- a/xen/include/xen/ioreq.h
+++ b/xen/include/xen/ioreq.h
@@ -118,7 +118,7 @@ bool arch_vcpu_ioreq_completion(enum vio_completion completion);
 static inline bool arch_vcpu_ioreq_completion(enum vio_completion completion)
 {
     ASSERT_UNREACHABLE();
-    return true;
+    return false;
 }
 #endif