diff --git a/docs/man/xl.cfg.pod.5 b/docs/man/xl.cfg.pod.5
index ead8a5c03e..fb8721faa3 100644
--- a/docs/man/xl.cfg.pod.5
+++ b/docs/man/xl.cfg.pod.5
@@ -470,6 +470,9 @@ the user to defined aliases which can be used by the guest kernel.
 Given the complexity of verifying the validity of a device tree, this
 option should only be used with trusted device tree.
 
+Note that the partial device tree should avoid to use the phandle 65000
+which is reserved by the toolstack.
+
 =back
 
 =head2 Devices
diff --git a/tools/libxl/libxl_arm.c b/tools/libxl/libxl_arm.c
index 71dbb9ee63..4fb5e26fab 100644
--- a/tools/libxl/libxl_arm.c
+++ b/tools/libxl/libxl_arm.c
@@ -81,10 +81,11 @@ static struct arch_info {
     {"xen-3.0-aarch64", "arm,armv8-timer", "arm,armv8" },
 };
 
-enum {
-    PHANDLE_NONE = 0,
-    PHANDLE_GIC,
-};
+/*
+ * The device tree compiler (DTC) is allocating the phandle from 1 to
+ * onwards. Reserve a high value for the GIC phandle.
+ */
+#define PHANDLE_GIC (65000)
 
 typedef uint32_t be32;
 typedef be32 gic_interrupt[3];
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index 4ea1290647..f1c62edfe0 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -416,6 +416,8 @@ libxl_domain_build_info = Struct("domain_build_info",[
     # Given the complexity of verifying the validity of a device tree,
     # libxl doesn't do any security check on it. It's the responsibility
     # of the caller to provide only trusted device tree.
+    # Note that the partial device tree should avoid to use the phandle
+    # 65000 which is reserved by the toolstack.
     ("device_tree",      string),
     ("u", KeyedUnion(None, libxl_domain_type, "type",
                 [("hvm", Struct(None, [("firmware",         string),