diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 2bbbc944a..8894bc936 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -4767,25 +4767,19 @@ static void SetActorRoll(AActor *activator, int tid, int angle, bool interpolate
 	}
 }
 
-static void SetActorTeleFog(AActor *activator, int tid, FName telefogsrc, FName telefogdest)
+static void SetActorTeleFog(AActor *activator, int tid, FString telefogsrc, FString telefogdest)
 {
-	//Simply put, if it doesn't exist, it won't change. One can use "" in this scenario.
-	const PClass *check;
+	// Set the actor's telefog to the specified actor. Handle "" as "don't
+	// change" since "None" should work just fine for disabling the fog (given
+	// that it will resolve to NAME_None which is not a valid actor name).
 	if (tid == 0)
 	{
 		if (activator != NULL)
 		{
-			check = PClass::FindClass(telefogsrc);
-			if (check == NULL || !stricmp(telefogsrc, "none") || !stricmp(telefogsrc, "null"))
-				activator->TeleFogSourceType = NULL;
-			else
-				activator->TeleFogSourceType = check;
-
-			check = PClass::FindClass(telefogdest);
-			if (check == NULL || !stricmp(telefogdest, "none") || !stricmp(telefogdest, "null"))
-				activator->TeleFogDestType = NULL;
-			else
-				activator->TeleFogDestType = check;
+			if (telefogsrc.IsNotEmpty())
+				activator->TeleFogSourceType = PClass::FindClass(telefogsrc);
+			if (telefogdest.IsNotEmpty())
+				activator->TeleFogDestType = PClass::FindClass(telefogdest);
 		}
 	}
 	else
@@ -4793,19 +4787,14 @@ static void SetActorTeleFog(AActor *activator, int tid, FName telefogsrc, FName
 		FActorIterator iterator(tid);
 		AActor *actor;
 
+		const PClass * const src = telefogsrc.IsNotEmpty() ? PClass::FindClass(telefogsrc) : NULL;
+		const PClass * const dest = telefogdest.IsNotEmpty() ? PClass::FindClass(telefogdest) : NULL;
 		while ((actor = iterator.Next()))
 		{
-			check = PClass::FindClass(telefogsrc);
-			if (check == NULL || !stricmp(telefogsrc, "none") || !stricmp(telefogsrc, "null"))
-				actor->TeleFogSourceType = NULL;
-			else
-				actor->TeleFogSourceType = check;
-
-			check = PClass::FindClass(telefogdest);
-			if (check == NULL || !stricmp(telefogdest, "none") || !stricmp(telefogdest, "null"))
-				actor->TeleFogDestType = NULL;
-			else
-				actor->TeleFogDestType = check;
+			if (telefogsrc.IsNotEmpty())
+				actor->TeleFogSourceType = src;
+			if (telefogdest.IsNotEmpty())
+				actor->TeleFogDestType = dest;
 		}
 	}
 }
diff --git a/src/thingdef/thingdef_properties.cpp b/src/thingdef/thingdef_properties.cpp
index 677979276..33066828c 100644
--- a/src/thingdef/thingdef_properties.cpp
+++ b/src/thingdef/thingdef_properties.cpp
@@ -1422,7 +1422,7 @@ DEFINE_PROPERTY(stamina, I, Actor)
 DEFINE_PROPERTY(telefogsourcetype, S, Actor)
 {
 	PROP_STRING_PARM(str, 0);
-	if (!stricmp(str, "") || (!stricmp(str, "none")) || (!stricmp(str, "null")) || *str == 0) defaults->TeleFogSourceType = NULL;
+	if (!stricmp(str, "") || !stricmp(str, "none")) defaults->TeleFogSourceType = NULL;
 	else defaults->TeleFogSourceType = FindClassTentative(str,"TeleportFog");
 }
 
@@ -1432,7 +1432,7 @@ DEFINE_PROPERTY(telefogsourcetype, S, Actor)
 DEFINE_PROPERTY(telefogdesttype, S, Actor)
 {
 	PROP_STRING_PARM(str, 0);
-	if (!stricmp(str, "") || (!stricmp(str, "none")) || (!stricmp(str, "null")) || *str == 0) defaults->TeleFogDestType = NULL;
+	if (!stricmp(str, "") || !stricmp(str, "none")) defaults->TeleFogDestType = NULL;
 	else defaults->TeleFogDestType = FindClassTentative(str, "TeleportFog");
 }