diff --git a/net/mac80211/ieee80211_ioctl.c b/net/mac80211/ieee80211_ioctl.c
index 8296e7de12c7a7cffcd7efe07afa7c5f2704cad9..d48f3aa30e306aa6f39d73fd8f4f3a3dffa68da3 100644
--- a/net/mac80211/ieee80211_ioctl.c
+++ b/net/mac80211/ieee80211_ioctl.c
@@ -821,7 +821,7 @@ static int ieee80211_ioctl_prism2_param(struct net_device *dev,
 		break;
 
 	case PRISM2_PARAM_PREAMBLE:
-		if (sdata->type != IEEE80211_IF_TYPE_AP) {
+		if (sdata->type == IEEE80211_IF_TYPE_AP) {
 			if (value)
 				sdata->flags |= IEEE80211_SDATA_SHORT_PREAMBLE;
 			else