Index: generic/nsf.c
===================================================================
diff -u -r4bd7db4eade02618a4822a959fb64abc8dabd3a7 -rc72f84a53588d33c939b6c59f018567d379ac750
--- generic/nsf.c	(.../nsf.c)	(revision 4bd7db4eade02618a4822a959fb64abc8dabd3a7)
+++ generic/nsf.c	(.../nsf.c)	(revision c72f84a53588d33c939b6c59f018567d379ac750)
@@ -27429,7 +27429,7 @@
       snprintf(buffer + i*2, sizeof(buffer) - (i+1)*2, "%.2x", (unsigned)(*((obj->bytes)+i) & 0xff));
     }
     if (objLength > NSF_DEBUG_SHOW_BYTES) {
-      strncat(buffer, trailer, sizeof(buffer) - strlen(buffer) - 1);
+      memmove(buffer, trailer, sizeof(buffer) - strlen(buffer) - 1);
     }
     Tcl_ListObjAppendElement(interp, resultObj, Tcl_NewStringObj(buffer, -1));