diff --git a/sc2/ChangeLog b/sc2/ChangeLog
index 7202e02d5..5a371dcc5 100644
--- a/sc2/ChangeLog
+++ b/sc2/ChangeLog
@@ -1,4 +1,7 @@
 Changes towards version 0.4:
+- Don't allow the reply "Symbionts, how interesting!" in the Supox
+  conversation until they mentioned they were Symbionts. (bug #528),
+  from Nic
 - Not initialising the various systems when -h/-? is supplied (bug #656),
   from Nic
 - F10 works when playing the intro (bug #665), from fOSSiL
diff --git a/sc2/src/sc2code/comm/supox/supoxc.c b/sc2/src/sc2code/comm/supox/supoxc.c
index 7d8e02844..a1b617022 100644
--- a/sc2/src/sc2code/comm/supox/supoxc.c
+++ b/sc2/src/sc2code/comm/supox/supoxc.c
@@ -447,9 +447,11 @@ NeutralSupox (RESPONSE_REF R)
 			break;
 		case 3:
 			pStr[0] = are_you_copying;
+			pStr[1] = 0;
 			break;
 		case 4:
 			pStr[0] = why_copy;
+			pStr[1] = 0;
 			break;
 	}
 	NumVisits = GET_GAME_STATE (ULTRON_CONDITION);