diff --git a/tlslite/keyexchange.py b/tlslite/keyexchange.py
index e25672cc..07bd7d7c 100644
--- a/tlslite/keyexchange.py
+++ b/tlslite/keyexchange.py
@@ -708,6 +708,11 @@ def makeServerKeyExchange(self, sigHash=None):
         ext_negotiated = ECPointFormat.uncompressed
         ext_c = self.clientHello.getExtension(ExtensionType.ec_point_formats)
         ext_s = self.serverHello.getExtension(ExtensionType.ec_point_formats)
+        if ext_c:
+            if ECPointFormat.uncompressed not in ext_c.formats:
+                raise TLSIllegalParameterException(
+                    "The client does not advertise "
+                    "the uncompressed point format extension.")
         if ext_c and ext_s:
             try:
                 ext_negotiated = next((i for i in ext_c.formats \