diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 8074a3a..d269e6f 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1441,6 +1441,16 @@
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_ALL ) );
 }
 
+/**
+ * Given a list of key exchange modes, check if at least one of them is
+ * supported.
+ *
+ * \param[in] ssl  SSL context
+ * \param key_modes_mask  Mask of the key exchange modes to check
+ *
+ * \return 0 if at least one of the key exchange modes is supported,
+ *         <>0 otherwise.
+ */
 static inline unsigned mbedtls_ssl_tls1_3_check_kex_modes( mbedtls_ssl_context *ssl,
                                                            int kex_modes_mask )
 {
@@ -1449,32 +1459,32 @@
 
 static inline int mbedtls_ssl_tls1_3_psk_enabled( mbedtls_ssl_context *ssl )
 {
-    return( mbedtls_ssl_tls1_3_check_kex_modes( ssl,
+    return( ! mbedtls_ssl_tls1_3_check_kex_modes( ssl,
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK ) );
 }
 
 static inline int mbedtls_ssl_tls1_3_psk_ephemeral_enabled(
                                                     mbedtls_ssl_context *ssl )
 {
-    return( mbedtls_ssl_tls1_3_check_kex_modes( ssl,
+    return( ! mbedtls_ssl_tls1_3_check_kex_modes( ssl,
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL ) );
 }
 
 static inline int mbedtls_ssl_tls1_3_ephemeral_enabled( mbedtls_ssl_context *ssl )
 {
-    return( mbedtls_ssl_tls1_3_check_kex_modes( ssl,
+    return( ! mbedtls_ssl_tls1_3_check_kex_modes( ssl,
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL ) );
 }
 
 static inline int mbedtls_ssl_tls1_3_some_ephemeral_enabled( mbedtls_ssl_context *ssl )
 {
-    return( mbedtls_ssl_tls1_3_check_kex_modes( ssl,
+    return( ! mbedtls_ssl_tls1_3_check_kex_modes( ssl,
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL_ALL ) );
 }
 
 static inline int mbedtls_ssl_tls1_3_some_psk_enabled( mbedtls_ssl_context *ssl )
 {
-    return( mbedtls_ssl_tls1_3_check_kex_modes( ssl,
+    return( ! mbedtls_ssl_tls1_3_check_kex_modes( ssl,
                    MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_ALL ) );
 }