diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 43443bf..5ba2f30 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -1020,11 +1020,6 @@
                           uint32_t *flags );
 #endif /* MBEDTLS_X509_CRT_PARSE_C */
 
-void mbedtls_ssl_write_version( int major, int minor, int transport,
-                        unsigned char ver[2] );
-void mbedtls_ssl_read_version( int *major, int *minor, int transport,
-                       const unsigned char ver[2] );
-
 static inline size_t mbedtls_ssl_in_hdr_len( const mbedtls_ssl_context *ssl )
 {
     return( (size_t) ( ssl->in_iv - ssl->in_hdr ) );
@@ -1104,6 +1099,69 @@
 #endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 || \
           MBEDTLS_SSL_PROTO_TLS1_2 */
 
+/*
+ * Convert version numbers to/from wire format
+ * and, for DTLS, to/from TLS equivalent.
+ *
+ * For TLS this is the identity.
+ * For DTLS, use 1's complement (v -> 255 - v, and then map as follows:
+ * 1.0 <-> 3.2      (DTLS 1.0 is based on TLS 1.1)
+ * 1.x <-> 3.x+1    for x != 0 (DTLS 1.2 based on TLS 1.2)
+ */
+static inline void mbedtls_ssl_write_version( int major, int minor,
+                                              int transport,
+                                              unsigned char ver[2] )
+{
+#if !defined(MBEDTLS_SSL_TRANSPORT__BOTH)
+    ((void) transport);
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( MBEDTLS_SSL_TRANSPORT_IS_DTLS( transport ) )
+    {
+        if( minor == MBEDTLS_SSL_MINOR_VERSION_2 )
+            --minor; /* DTLS 1.0 stored as TLS 1.1 internally */
+
+        ver[0] = (unsigned char)( 255 - ( major - 2 ) );
+        ver[1] = (unsigned char)( 255 - ( minor - 1 ) );
+    }
+    MBEDTLS_SSL_TRANSPORT_ELSE
+#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS)
+    {
+        ver[0] = (unsigned char) major;
+        ver[1] = (unsigned char) minor;
+    }
+#endif
+}
+
+static inline void mbedtls_ssl_read_version( int *major, int *minor,
+                                             int transport,
+                                             const unsigned char ver[2] )
+{
+#if !defined(MBEDTLS_SSL_TRANSPORT__BOTH)
+    ((void) transport);
+#endif
+
+#if defined(MBEDTLS_SSL_PROTO_DTLS)
+    if( MBEDTLS_SSL_TRANSPORT_IS_DTLS( transport ) )
+    {
+        *major = 255 - ver[0] + 2;
+        *minor = 255 - ver[1] + 1;
+
+        if( *minor == MBEDTLS_SSL_MINOR_VERSION_1 )
+            ++*minor; /* DTLS 1.0 stored as TLS 1.1 internally */
+    }
+    MBEDTLS_SSL_TRANSPORT_ELSE
+#endif /* MBEDTLS_SSL_PROTO_DTLS */
+#if defined(MBEDTLS_SSL_PROTO_TLS)
+    {
+        *major = ver[0];
+        *minor = ver[1];
+    }
+#endif /* MBEDTLS_SSL_PROTO_TLS */
+}
+
 #ifdef __cplusplus
 }
 #endif