--- functions_org.c	2015-11-06 10:21:40.707992184 +0530
+++ functions.c	2015-11-06 10:22:32.027993502 +0530
@@ -301,6 +301,12 @@
     func = (exsltFuncFunctionData*) xmlHashLookup2 (data->funcs,
 						    ctxt->context->functionURI,
 						    ctxt->context->function);
+    if (func ==  NULL) {
+        xsltGenericError(xsltGenericErrorContext,
+                         "{%s}%s: not found\n",
+                         ctxt->context->functionURI, ctxt->context->function);
+        return;
+    }
 
     /*
      * params handling
