Index: openacs-4/packages/acs-tcl/tcl/utilities-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/utilities-procs.tcl,v
diff -u -N -r1.189.2.2 -r1.189.2.3
--- openacs-4/packages/acs-tcl/tcl/utilities-procs.tcl	15 Feb 2019 13:25:58 -0000	1.189.2.2
+++ openacs-4/packages/acs-tcl/tcl/utilities-procs.tcl	18 Feb 2019 13:13:16 -0000	1.189.2.3
@@ -995,7 +995,14 @@
                 }
             }
             default {
-                error "invalid value '$key' in sign() specification"
+                #
+                # It seems, there are several cases, where
+                # "export_vars_sign" is called with invalid params
+                # (which can be seemingly ignored:
+                #
+                ns_log warning  "export_vars_sign: invalid value '$key' in sign() specification (params <$params>, key=<$key>)"
+                #error "invalid value '$key' in sign() specification"
+
             }
         }
     }