diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index b332822355..e2b19d2f44 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -2136,6 +2136,7 @@
 #error "POLARSSL_ECDSA_DETERMINISTIC defined, but not all prerequisites"
 #endif
 
+/* For now, M255 (aka Curve25519) can't be the only curve. */
 #if defined(POLARSSL_ECP_C) && ( !defined(POLARSSL_BIGNUM_C) || (   \
     !defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) &&                  \
     !defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) &&                  \
@@ -2145,7 +2146,6 @@
     !defined(POLARSSL_ECP_DP_BP256R1_ENABLED)   &&                  \
     !defined(POLARSSL_ECP_DP_BP384R1_ENABLED)   &&                  \
     !defined(POLARSSL_ECP_DP_BP512R1_ENABLED)   &&                  \
-    !defined(POLARSSL_ECP_DP_M255_ENABLED)      &&                  \
     !defined(POLARSSL_ECP_DP_SECP192K1_ENABLED) &&                  \
     !defined(POLARSSL_ECP_DP_SECP224K1_ENABLED) &&                  \
     !defined(POLARSSL_ECP_DP_SECP256K1_ENABLED) ) )