diff --git a/include/mbedtls/config_adjust_legacy_crypto.h b/include/mbedtls/config_adjust_legacy_crypto.h
index 696266c..833f152 100644
--- a/include/mbedtls/config_adjust_legacy_crypto.h
+++ b/include/mbedtls/config_adjust_legacy_crypto.h
@@ -400,6 +400,13 @@
 #define MBEDTLS_SHA256_USE_ARMV8_A_CRYPTO_ONLY
 #endif
 
+/* psa_util file features some ECDSA conversion functions, to convert between
+ * legacy's ASN.1 DER format and PSA's raw one. */
+#if defined(MBEDTLS_ECDSA_C) || defined(MBEDTLS_PSA_CRYPTO_C) && \
+    (defined(PSA_WANT_ALG_ECDSA) || defined(PSA_WANT_ALG_DETERMINISTIC_ECDSA))
+#define MBEDTLS_PSA_UTIL_HAVE_ECDSA
+#endif
+
 /* Some internal helpers to determine which keys are availble. */
 #if (!defined(MBEDTLS_USE_PSA_CRYPTO) && defined(MBEDTLS_AES_C)) || \
     (defined(MBEDTLS_USE_PSA_CRYPTO) && defined(PSA_WANT_KEY_TYPE_AES))
diff --git a/include/mbedtls/psa_util.h b/include/mbedtls/psa_util.h
index 93fb38d..3bf05d1 100644
--- a/include/mbedtls/psa_util.h
+++ b/include/mbedtls/psa_util.h
@@ -182,6 +182,8 @@
 }
 #endif /* MBEDTLS_PSA_CRYPTO_C */
 
+#if defined(MBEDTLS_PSA_UTIL_HAVE_ECDSA)
+
 #if defined(MBEDTLS_ASN1_WRITE_C)
 /** Convert an ECDSA signature from raw format (used by PSA APIs) to DER ASN.1
  * format (used by legacy crypto APIs).
@@ -220,6 +222,8 @@
                              size_t bits);
 #endif /* MBEDTLS_ASN1_PARSE_C */
 
+#endif /* MBEDTLS_PSA_UTIL_HAVE_ECDSA */
+
 /**@}*/
 
 #endif /* MBEDTLS_PSA_UTIL_H */