diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index bae772a..4c7f9d0 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5980,19 +5980,21 @@
     }
 
     /*
-     * Read and optionally decrypt the message contents
+     * Make sure the entire record contents are available.
+     *
+     * In TLS, this means fetching them from the underlying transport.
+     * In DTLS, it means checking that the incoming datagram is large enough.
      */
-    if( ( ret = mbedtls_ssl_fetch_input( ssl,
-                                 mbedtls_ssl_in_hdr_len( ssl ) + ssl->in_msglen ) ) != 0 )
-    {
-        MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_fetch_input", ret );
-        return( ret );
-    }
-
-    /* Done reading this record, get ready for the next one */
 #if defined(MBEDTLS_SSL_PROTO_DTLS)
     if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
     {
+        if( ssl->in_left < mbedtls_ssl_in_hdr_len( ssl ) + ssl->in_msglen )
+        {
+            MBEDTLS_SSL_DEBUG_MSG( 1, ( "Datagram too small to contain record." ) );
+            return( MBEDTLS_ERR_SSL_INVALID_RECORD );
+        }
+
+        /* Remember offset of next record within datagram. */
         ssl->next_record_offset = ssl->in_msglen + mbedtls_ssl_in_hdr_len( ssl );
         if( ssl->next_record_offset < ssl->in_left )
         {
@@ -6001,7 +6003,21 @@
     }
     else
 #endif
+    {
+        ret = mbedtls_ssl_fetch_input( ssl,
+                              mbedtls_ssl_in_hdr_len( ssl ) + ssl->in_msglen );
+        if( ret != 0 )
+        {
+            MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_fetch_input", ret );
+            return( ret );
+        }
+
         ssl->in_left = 0;
+    }
+
+    /*
+     * Decrypt record contents.
+     */
 
     if( ( ret = ssl_prepare_record_content( ssl ) ) != 0 )
     {