diff --git a/include/psa/crypto_sizes.h b/include/psa/crypto_sizes.h
index 1b46c567f4..8fd91ff285 100644
--- a/include/psa/crypto_sizes.h
+++ b/include/psa/crypto_sizes.h
@@ -987,8 +987,11 @@
  *
  * See also #PSA_RAW_KEY_AGREEMENT_OUTPUT_SIZE(\p key_type, \p key_bits).
  */
-#define PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE   \
-    (PSA_BITS_TO_BYTES(PSA_VENDOR_FFDH_MAX_KEY_BITS))
+#define PSA_RAW_KEY_AGREEMENT_OUTPUT_MAX_SIZE             \
+    (PSA_BITS_TO_BYTES(PSA_VENDOR_ECC_MAX_CURVE_BITS) >   \
+     PSA_BITS_TO_BYTES(PSA_VENDOR_FFDH_MAX_KEY_BITS) ?    \
+     PSA_BITS_TO_BYTES(PSA_VENDOR_ECC_MAX_CURVE_BITS) :   \
+     PSA_BITS_TO_BYTES(PSA_VENDOR_FFDH_MAX_KEY_BITS))
 
 /** The default IV size for a cipher algorithm, in bytes.
  *