diff --git a/library/ecdh.c b/library/ecdh.c
index c5726877d..30c5f9f7f 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -637,6 +637,10 @@ static int ecdh_calc_secret_internal( mbedtls_ecdh_context_mbed *ctx,
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
+
+    if( ctx->grp.id == MBEDTLS_ECP_DP_CURVE25519 )
+        return mbedtls_mpi_write_binary_le( &ctx->z, buf, *olen );
+
     return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
 }
 
diff --git a/tests/suites/test_suite_ecdh.data b/tests/suites/test_suite_ecdh.data
index af25359d3..fb4a232fc 100644
--- a/tests/suites/test_suite_ecdh.data
+++ b/tests/suites/test_suite_ecdh.data
@@ -88,6 +88,18 @@ ECDH calc_secret: theirs first, SECP256R1 (RFC 5903)
 depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_SECP256R1:"c6ef9c5d78ae012a011164acb397ce2088685d8f06bf9be0b283ab46476bee53":"04dad0b65394221cf9b051e1feca5787d098dfe637fc90b9ef945d0c37725811805271a0461cdb8252d61f1c456fa3e59ab1f45b33accf5f58389e0577b8990bb3":1:"d6840f6b42f6edafd13116e0e12565202fef8e9ece7dce03812464d04b9442de"
 
+ecdh calc_secret: ours first (Alice), curve25519 (rfc 7748)
+depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
+ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_CURVE25519:"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a":"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f":0:"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742"
+
+ecdh calc_secret: theirs first (Alice), curve25519 (rfc 7748)
+depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
+ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_CURVE25519:"77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a":"de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f":1:"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742"
+
+ecdh calc_secret: ours first (Bob), curve25519 (rfc 7748)
+depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
+ecdh_exchange_calc_secret:MBEDTLS_ECP_DP_CURVE25519:"5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb":"8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a":0:"4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742"
+
 ECDH get_params with mismatched groups: our BP256R1, their SECP256R1
 depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECP_DP_BP256R1_ENABLED
 ecdh_exchange_get_params_fail:MBEDTLS_ECP_DP_BP256R1:"1234567812345678123456781234567812345678123456781234567812345678":MBEDTLS_ECP_DP_SECP256R1:"04dad0b65394221cf9b051e1feca5787d098dfe637fc90b9ef945d0c37725811805271a0461cdb8252d61f1c456fa3e59ab1f45b33accf5f58389e0577b8990bb3":0:MBEDTLS_ERR_ECP_BAD_INPUT_DATA