Document dependency of ECDSA_DETERMINISTIC on MD_C
diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index f4f5f77..cf7edf0 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -286,6 +286,8 @@
  * may result in a compromise of the long-term signing key. This is avoided by
  * the deterministic variant.
  *
+ * Requires: POLARSSL_MD_C
+ *
  * Comment this macro to disable deterministic ECDSA.
  */
 #define POLARSSL_ECDSA_DETERMINISTIC
@@ -1945,6 +1947,10 @@
 #error "POLARSSL_ECDSA_C defined, but not all prerequisites"
 #endif
 
+#if defined(POLARSSL_ECDSA_DETERMINISTIC) && !defined(POLARSSL_MD_C)
+#error "POLARSSL_ECDSA_DETERMINISTIC defined, but not all prerequisites"
+#endif
+
 #if defined(POLARSSL_ECP_C) && ( !defined(POLARSSL_BIGNUM_C) || (   \
     !defined(POLARSSL_ECP_DP_SECP192R1_ENABLED) &&                  \
     !defined(POLARSSL_ECP_DP_SECP224R1_ENABLED) &&                  \