diff --git a/keymaster/4.0/vts/functional/KeymasterHidlTest.cpp b/keymaster/4.0/vts/functional/KeymasterHidlTest.cpp
index d0ad433..d326334 100644
--- a/keymaster/4.0/vts/functional/KeymasterHidlTest.cpp
+++ b/keymaster/4.0/vts/functional/KeymasterHidlTest.cpp
@@ -21,6 +21,7 @@
 
 #include <android-base/logging.h>
 #include <android/hidl/manager/1.0/IServiceManager.h>
+#include <cutils/properties.h>
 
 #include <keymasterV4_0/key_param_output.h>
 #include <keymasterV4_0/keymaster_utils.h>
@@ -685,6 +686,9 @@
             case Algorithm::EC:
                 return {224, 384, 521};
             case Algorithm::AES:
+                // The HAL language was clarified to exclude AES key sizes of 192 for StrongBox
+                // instances on devices launched on API Level 31 and above.
+                if (property_get_int32("ro.board.first_api_level", 0) < 31) return {};
                 return {192};
             default:
                 return {};
diff --git a/security/keymint/aidl/android/hardware/security/keymint/IKeyMintDevice.aidl b/security/keymint/aidl/android/hardware/security/keymint/IKeyMintDevice.aidl
index 2241735..4e81e71 100644
--- a/security/keymint/aidl/android/hardware/security/keymint/IKeyMintDevice.aidl
+++ b/security/keymint/aidl/android/hardware/security/keymint/IKeyMintDevice.aidl
@@ -96,7 +96,8 @@
  *
  * o   AES
  *
- *      - 128 and 256-bit keys
+ *      - TRUSTED_ENVIRONMENT IKeyMintDevices must support 128, 192 and 256-bit keys.
+ *        STRONGBOX IKeyMintDevices must only support 128 and 256-bit keys.
  *      - CBC, CTR, ECB and GCM modes.  The GCM mode must not allow the use of tags smaller than 96
  *        bits or nonce lengths other than 96 bits.
  *      - CBC and ECB modes must support unpadded and PKCS7 padding modes.  With no padding CBC and