diff --git a/drivers/bus/isapnp/isapnp.c b/drivers/bus/isapnp/isapnp.c
index e8862345cc0..f810532921e 100644
--- a/drivers/bus/isapnp/isapnp.c
+++ b/drivers/bus/isapnp/isapnp.c
@@ -80,7 +80,7 @@ IsaFdoCreateDeviceIDs(
                                   TempString.MaximumLength / sizeof(WCHAR),
                                   &End,
                                   NULL, 0,
-                                  L"ISAPNP\\%3S%04X",
+                                  L"ISAPNP\\%.3S%04x",
                                   LogDev->VendorId,
                                   LogDev->ProdId);
     if (!NT_SUCCESS(Status))
@@ -98,8 +98,8 @@ IsaFdoCreateDeviceIDs(
                                   TempString.MaximumLength / sizeof(WCHAR),
                                   &End,
                                   NULL, 0,
-                                  L"ISAPNP\\%3S%04X@"
-                                  L"*%3S%04X@",
+                                  L"ISAPNP\\%.3S%04x@"
+                                  L"*%.3S%04x@",
                                   LogDev->VendorId,
                                   LogDev->ProdId,
                                   LogDev->VendorId,
diff --git a/drivers/bus/isapnp/pdo.c b/drivers/bus/isapnp/pdo.c
index 7cd8c7d3812..6651cc54710 100644
--- a/drivers/bus/isapnp/pdo.c
+++ b/drivers/bus/isapnp/pdo.c
@@ -59,7 +59,7 @@ IsaPdoQueryCapabilities(
 
     if (LogDev)
     {
-        DeviceCapabilities->UniqueID = LogDev->SerialNumber != 0xffffffff;
+        DeviceCapabilities->UniqueID = TRUE;
         DeviceCapabilities->Address = LogDev->CSN;
     }
     else