diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 29de49351d..a4c7d64223 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -68,6 +68,19 @@ configurations (e.g. -smp drawers=1,books=1,clusters=1 for x86 PC machine) is
 marked deprecated since 9.0, users have to ensure that all the topology members
 described with -smp are supported by the target machine.
 
+``-old-param`` option for booting Arm kernels via param_struct (since 10.0)
+'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+The ``-old-param`` command line option is specific to Arm targets:
+it is used when directly booting a guest kernel to pass it the
+command line and other information via the old ``param_struct`` ABI,
+rather than the newer ATAGS or DTB mechanisms. This option was only
+ever needed to support ancient kernels on some old board types
+like the ``akita`` or ``terrier``; it has been deprecated in the
+kernel since 2001. None of the board types QEMU supports need
+``param_struct`` support, so this option has been deprecated and will
+be removed in a future QEMU version.
+
 User-mode emulator command line arguments
 -----------------------------------------
 
diff --git a/system/vl.c b/system/vl.c
index db8e604eba..aa91047c48 100644
--- a/system/vl.c
+++ b/system/vl.c
@@ -3469,6 +3469,7 @@ void qemu_init(int argc, char **argv)
                 nb_prom_envs++;
                 break;
             case QEMU_OPTION_old_param:
+                warn_report("-old-param is deprecated");
                 old_param = 1;
                 break;
             case QEMU_OPTION_rtc: