diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index d52026e..c4b8995 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -2638,13 +2638,24 @@
 //#define MBEDTLS_X509_MAX_FILE_PATH_LEN     512 /**< Maximum length of a path/filename string in bytes including the null terminator character ('\0'). */
 
 /**
- * Allow SHA-1 in the default TLS configuration for certificate signing and
- * TLS 1.2 handshake signature. Without this build-time option, SHA-1
- * support must be activated explicitly through mbedtls_ssl_conf_cert_profile
- * and mbedtls_ssl_conf_sig_hashes. The use of SHA-1 in TLS <= 1.1 and in
- * HMAC-SHA-1 for XXX_SHA ciphersuites is always allowed by default.
+ * Allow SHA-1 in the default TLS configuration for certificate signing.
+ * Without this build-time option, SHA-1 support must be activated explicitly
+ * through mbedtls_ssl_conf_cert_profile. Turning on this option is not
+ * recommended because of it is possible to generte SHA-1 collisions, however
+ * this may be safe for legacy infrastructure where additional controls apply.
  */
-// #define MBEDTLS_TLS_DEFAULT_ALLOW_SHA1
+// #define MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES
+
+/**
+ * Allow SHA-1 in the default TLS configuration for TLS 1.2 handshake
+ * signature and ciphersuite selection. Without this build-time option, SHA-1
+ * support must be activated explicitly through mbedtls_ssl_conf_sig_hashes.
+ * The use of SHA-1 in TLS <= 1.1 and in HMAC-SHA-1 is always allowed by
+ * default. At the time of writing, there is no practical attack on the use
+ * of SHA-1 in handshake signatures, hence this option is turned on by default
+ * for compatibility with existing peers.
+ */
+#define MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_KEY_EXCHANGE
 
 /* \} name SECTION: Customisation configuration options */