diff --git a/src/thingdef/thingdef_codeptr.cpp b/src/thingdef/thingdef_codeptr.cpp
index 77205ba13..7435bc6fe 100644
--- a/src/thingdef/thingdef_codeptr.cpp
+++ b/src/thingdef/thingdef_codeptr.cpp
@@ -4039,7 +4039,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_ScaleVelocity)
 		return;
 	}
 
-	INTBOOL was_moving = self->velx | self->vely | self->velz;
+	INTBOOL was_moving = ref->velx | ref->vely | ref->velz;
 
 	ref->velx = FixedMul(ref->velx, scale);
 	ref->vely = FixedMul(ref->vely, scale);
@@ -4061,7 +4061,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_ScaleVelocity)
 
 DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_ChangeVelocity)
 {
-	ACTION_PARAM_START(4);
+	ACTION_PARAM_START(5);
 	ACTION_PARAM_FIXED(x, 0);
 	ACTION_PARAM_FIXED(y, 1);
 	ACTION_PARAM_FIXED(z, 2);
@@ -4102,7 +4102,7 @@ DEFINE_ACTION_FUNCTION_PARAMS(AActor, A_ChangeVelocity)
 
 	if (was_moving)
 	{
-		CheckStopped(self);
+		CheckStopped(ref);
 	}
 }