diff --git a/src/ca/client/access.cpp b/src/ca/client/access.cpp
index a36899c02..ec873dd5b 100644
--- a/src/ca/client/access.cpp
+++ b/src/ca/client/access.cpp
@@ -605,7 +605,7 @@ void epicsShareAPI ca_signal_formated ( long ca_status, const char *pfilenm,
     }
     else {
         fprintf ( stderr, "CA exception in thread w/o CA ctx: status=%s file=%s line=%d: \n",
-            ca_message ( ca_status ), pfilenm, lineno );
+            ca_message ( ca_status ), pfilenm ? pfilenm : "<null>", lineno );
         if ( pFormat ) {
             vfprintf ( stderr, pFormat, theArgs );
         }