diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index df1d4355b157feacafd2a72633a67e15dd0de7e1..f5cf1f153855b5fc91d0b43a918f5c5461ea82fe 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -6851,7 +6851,7 @@ static int qemudDomainAttachSCSIDisk(struct qemud_driver *driver,
 {
     int i;
     qemuDomainObjPrivatePtr priv = vm->privateData;
-    virDomainControllerDefPtr cont;
+    virDomainControllerDefPtr cont = NULL;
     char *drivestr = NULL;
     char *devstr = NULL;
     int ret = -1;
@@ -6894,6 +6894,11 @@ static int qemudDomainAttachSCSIDisk(struct qemud_driver *driver,
             goto error;
     }
 
+    /* Tell clang that "cont" is non-NULL.
+       This is because disk->info.addr.driver.controller is unsigned,
+       and hence the above loop must iterate at least once.  */
+    sa_assert (cont);
+
     if (cont->info.type != VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI) {
         qemuReportError(VIR_ERR_INTERNAL_ERROR,
                         _("SCSI controller %d was missing its PCI address"), cont->idx);