diff --git a/src/util/virpci.c b/src/util/virpci.c
index c3d211f64b..00d106441b 100644
--- a/src/util/virpci.c
+++ b/src/util/virpci.c
@@ -1327,6 +1327,8 @@ virPCIDeviceDetach(virPCIDevicePtr dev,
                    virPCIDeviceList *activeDevs,
                    virPCIDeviceList *inactiveDevs)
 {
+    sa_assert(dev->stubDriver);
+
     if (virPCIProbeStubDriver(dev->stubDriver) < 0)
         return -1;
 
@@ -1657,7 +1659,7 @@ int
 virPCIDeviceSetStubDriver(virPCIDevicePtr dev, const char *driver)
 {
     VIR_FREE(dev->stubDriver);
-    return driver ? VIR_STRDUP(dev->stubDriver, driver) : 0;
+    return VIR_STRDUP(dev->stubDriver, driver);
 }
 
 const char *
diff --git a/src/util/virpci.h b/src/util/virpci.h
index 42c3c957e2..ac6dae18e0 100644
--- a/src/util/virpci.h
+++ b/src/util/virpci.h
@@ -63,7 +63,8 @@ void virPCIDeviceSetManaged(virPCIDevice *dev,
                             bool managed);
 unsigned int virPCIDeviceGetManaged(virPCIDevice *dev);
 int virPCIDeviceSetStubDriver(virPCIDevicePtr dev,
-                              const char *driver);
+                              const char *driver)
+    ATTRIBUTE_NONNULL(2);
 const char *virPCIDeviceGetStubDriver(virPCIDevicePtr dev);
 void virPCIDeviceSetUsedBy(virPCIDevice *dev,
                            const char *used_by);