diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index d076c2352..93de091c4 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -546,6 +546,23 @@
 #error "MBEDTLS_SSL_PROTO_TLS1_2 defined, but not all prerequisites"
 #endif
 
+#if (defined(MBEDTLS_SSL_PROTO_SSL3) || defined(MBEDTLS_SSL_PROTO_TLS1) ||  \
+     defined(MBEDTLS_SSL_PROTO_TLS1_1) || defined(MBEDTLS_SSL_PROTO_TLS1_2)) && \
+    !(defined(MBEDTLS_KEY_EXCHANGE_RSA_ENABLED) ||                          \
+      defined(MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED) ||                    \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED) ||                  \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED) ||                     \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED) ||                   \
+      defined(MBEDTLS_KEY_EXCHANGE_PSK_ENABLED) ||                          \
+      defined(MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED) ||                      \
+      defined(MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED) ||                    \
+      defined(MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED) )
+#error "One or more versions of the TLS protocol are enabled " \
+        "but no key exchange methods defined with MBEDTLS_KEY_EXCHANGE_xxxx"
+#endif
+
 #if defined(MBEDTLS_SSL_PROTO_DTLS)     && \
     !defined(MBEDTLS_SSL_PROTO_TLS1_1)  && \
     !defined(MBEDTLS_SSL_PROTO_TLS1_2)
@@ -669,6 +686,10 @@
 #error "MBEDTLS_X509_CREATE_C defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_CERTS_C) && !defined(MBEDTLS_X509_USE_C)
+#error "MBEDTLS_CERTS_C defined, but not all prerequisites"
+#endif
+
 #if defined(MBEDTLS_X509_CRT_PARSE_C) && ( !defined(MBEDTLS_X509_USE_C) )
 #error "MBEDTLS_X509_CRT_PARSE_C defined, but not all prerequisites"
 #endif
diff --git a/library/x509.c b/library/x509.c
index 2e0b0e8f6..4d2530320 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -1063,7 +1063,7 @@ cleanup:
     mbedtls_x509_crt_free( &clicert );
 #else
     ((void) verbose);
-#endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA1_C */
+#endif /* MBEDTLS_CERTS_C && MBEDTLS_SHA256_C */
     return( ret );
 }