diff --git a/alibuild_helpers/args.py b/alibuild_helpers/args.py
index 28826a3e..eacea092 100644
--- a/alibuild_helpers/args.py
+++ b/alibuild_helpers/args.py
@@ -380,6 +380,9 @@ def matchValidArch(architecture):
    Fedora 33 compatible: fedora33_x86-64
    Fedora 34 compatible: fedora34_x86-64
 
+On Linux, ARM:
+   RHEL9 / ALMA9 compatible: slc9_aarch64
+
 On Linux, POWER8 / PPC64 (little endian):
    RHEL7 / CC7 compatible: slc7_ppc64
 
@@ -389,7 +392,7 @@ def matchValidArch(architecture):
 """
 
 # When updating this variable, also update docs/user.markdown!
-S3_SUPPORTED_ARCHS = "slc7_x86-64", "slc8_x86-64", "ubuntu2004_x86-64", "ubuntu2204_x86-64", "slc9_x86-64"
+S3_SUPPORTED_ARCHS = "slc7_x86-64", "slc8_x86-64", "ubuntu2004_x86-64", "ubuntu2204_x86-64", "slc9_x86-64", "slc9_aarch64"
 
 def finaliseArgs(args, parser):