diff --git a/src/k_terrain.c b/src/k_terrain.c
index 666cc9e53..a065827aa 100644
--- a/src/k_terrain.c
+++ b/src/k_terrain.c
@@ -502,7 +502,7 @@ void K_ProcessTerrainEffect(mobj_t *mo)
 	{
 		UINT8 dmg = (terrain->damageType & 0xFF);
 
-		if (dmg & DMG_STUMBLE && !G_CompatLevel(0x0010))
+		if ((dmg == DMG_STUMBLE) && !G_CompatLevel(0x0010))
 		{
 			if (player->mo->hitlag == 0 &&
 				(player->mo->momz == 0 || (player->mo->momz > 0) != (P_MobjFlip(player->mo) > 0)))