diff --git a/src/openvpn/ssl_mbedtls.c b/src/openvpn/ssl_mbedtls.c
index 85c771a..8a0f7d2 100644
--- a/src/openvpn/ssl_mbedtls.c
+++ b/src/openvpn/ssl_mbedtls.c
@@ -450,6 +450,12 @@
         }
     }
 
+    /* Check if any groups were valid. */
+    if (i == 0)
+    {
+        msg(M_FATAL, "Error: All groups in \"%s\" are invalid or unsupported.", groups);
+    }
+
     /* Recent mbedtls versions state that the list of groups must be terminated
      * with 0. Older versions state that it must be terminated with MBEDTLS_ECP_DP_NONE
      * which is also 0, so this works either way. */