diff --git a/doc/fixes34.4 b/doc/fixes34.4
index 9fbb077a1..2b144909b 100644
--- a/doc/fixes34.4
+++ b/doc/fixes34.4
@@ -46,6 +46,7 @@ handle lava when removing or losing water walking boots
 fix incomplete sentence occuring when unique monster's corpse fell down stairs
 fractured boulders or statues produced inconsistent object settings on the
 	resulting rocks
+really fix rolling boulder bug C340-18, the previous "fix" reversed the test
 
 
 Platform- and/or Interface-Specific Fixes
diff --git a/src/mthrowu.c b/src/mthrowu.c
index 3fbc6c862..b6d25b988 100644
--- a/src/mthrowu.c
+++ b/src/mthrowu.c
@@ -206,7 +206,7 @@ boolean verbose;  /* give message(s) even when you can't see what happened */
 			? "destroyed" : "killed");
 		/* don't blame hero for unknown rolling boulder trap */
 		if (!context.mon_moving &&
-		    (otmp->otyp != BOULDER || range >= 0 || !otmp->otrapped))
+		    (otmp->otyp != BOULDER || range >= 0 || otmp->otrapped))
 		    xkilled(mtmp,0);
 		else mondied(mtmp);
 	    }