diff --git a/include/psa/crypto_sizes.h b/include/psa/crypto_sizes.h
index eeb460eb6f..4f4a187eba 100644
--- a/include/psa/crypto_sizes.h
+++ b/include/psa/crypto_sizes.h
@@ -645,6 +645,11 @@
 #undef PSA_SIGNATURE_MAX_SIZE
 #define PSA_SIGNATURE_MAX_SIZE      PSA_BITS_TO_BYTES(PSA_VENDOR_RSA_MAX_KEY_BITS)
 #endif
+#if defined(PSA_WANT_KEY_TYPE_DH_KEY_PAIR_BASIC) && \
+    (PSA_BITS_TO_BYTES(PSA_VENDOR_FFDH_MAX_KEY_BITS) > PSA_SIGNATURE_MAX_SIZE)
+#undef PSA_SIGNATURE_MAX_SIZE
+#define PSA_SIGNATURE_MAX_SIZE      PSA_BITS_TO_BYTES(PSA_VENDOR_FFDH_MAX_KEY_BITS)
+#endif
 
 /** Sufficient output buffer size for psa_asymmetric_encrypt().
  *