diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index a86212679..69f489627 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -4760,10 +4760,15 @@ static void SetActorTeleFog(AActor *activator, int tid, FName telefogsrc, FName
 		if (activator != NULL)
 		{
 			check = PClass::FindClass(telefogsrc);
-			if (check != NULL)
+			if (check != NULL || !stricmp(telefogsrc, "none") || !stricmp(telefogsrc, "null"))
+				activator->TeleFogSourceType = NULL;
+			else
 				activator->TeleFogSourceType = check;
+
 			check = PClass::FindClass(telefogdest);
-			if (check != NULL)
+			if (check != NULL || !stricmp(telefogdest, "none") || !stricmp(telefogdest, "null"))
+				activator->TeleFogDestType = NULL;
+			else
 				activator->TeleFogDestType = check;
 		}
 	}
@@ -4775,10 +4780,15 @@ static void SetActorTeleFog(AActor *activator, int tid, FName telefogsrc, FName
 		while ((actor = iterator.Next()))
 		{
 			check = PClass::FindClass(telefogsrc);
-			if (check != NULL)
+			if (check != NULL || !stricmp(telefogsrc, "none") || !stricmp(telefogsrc, "null"))
+				actor->TeleFogSourceType = NULL;
+			else
 				actor->TeleFogSourceType = check;
+
 			check = PClass::FindClass(telefogdest);
-			if (check != NULL)
+			if (check != NULL || !stricmp(telefogdest, "none") || !stricmp(telefogdest, "null"))
+				actor->TeleFogDestType = NULL;
+			else
 				actor->TeleFogDestType = check;
 		}
 	}