diff --git a/library/ecdsa.c b/library/ecdsa.c
old mode 100644
new mode 100755
index 2daabee..f346526
--- a/library/ecdsa.c
+++ b/library/ecdsa.c
@@ -263,9 +263,7 @@
     mbedtls_mpi *pk = &k, *pr = r;
 
     /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
-    if( grp->id == MBEDTLS_ECP_DP_CURVE25519 ||
-        grp->id == MBEDTLS_ECP_DP_CURVE448 ||
-        grp->N.p == NULL )
+    if( !mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     /* Make sure d is in range 1..n-1 */
@@ -380,6 +378,20 @@
     return( ret );
 }
 
+int mbedtls_ecdsa_can_do( mbedtls_ecp_group_id gid )
+{
+    switch( gid )
+    {
+#ifdef MBEDTLS_ECP_DP_CURVE25519_ENABLED
+    case MBEDTLS_ECP_DP_CURVE25519: return 0;
+#endif
+#ifdef MBEDTLS_ECP_DP_CURVE448_ENABLED
+    case MBEDTLS_ECP_DP_CURVE448: return 0;
+#endif
+    default: return 1;
+    }
+}
+
 /*
  * Compute ECDSA signature of a hashed message
  */
@@ -504,7 +516,7 @@
     mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
 
     /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
-    if( grp->N.p == NULL )
+    if( !mbedtls_ecdsa_can_do( grp->id ) || grp->N.p == NULL )
         return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 
     ECDSA_RS_ENTER( ver );