diff --git a/src/p_local.h b/src/p_local.h
index b0c22767b..23de23c85 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -64,6 +64,7 @@
 typedef enum{
 	THINK_POLYOBJ,
 	THINK_MAIN,
+	THINK_DYNSLOPE,
 	THINK_MOBJ,
 	NUM_THINKERLISTS
 } thinklistnum_t; /**< Thinker lists. */
diff --git a/src/p_slopes.c b/src/p_slopes.c
index 6aee9fcff..e4b41419d 100644
--- a/src/p_slopes.c
+++ b/src/p_slopes.c
@@ -171,7 +171,7 @@ static inline void P_AddDynSlopeThinker (pslope_t* slope, dynplanetype_t type, l
 	th->slope = slope;
 	th->type = type;
 
-	P_AddThinker(THINK_MAIN, &th->thinker);
+	P_AddThinker(THINK_DYNSLOPE, &th->thinker);
 }