diff --git a/src/Input.c b/src/Input.c
index 9dc8c2290..e184d5bdb 100644
--- a/src/Input.c
+++ b/src/Input.c
@@ -738,6 +738,10 @@ void InputHandler_PlaceBlock(void) {
 	if (Game_CanPick(old) || !Blocks.CanPlace[block]) return;
 	/* air-ish blocks can only replace over other air-ish blocks */
 	if (Blocks.Draw[block] == DRAW_GAS && Blocks.Draw[old] != DRAW_GAS) return;
+
+	/* undeletable gas blocks can't be replaced with other blocks */
+	if (Blocks.Collide[old] == COLLIDE_GAS && !Blocks.CanDelete[old]) return;
+
 	if (!CheckIsFree(block)) return;
 
 	Game_ChangeBlock(pos.X, pos.Y, pos.Z, block);
diff --git a/src/Server.c b/src/Server.c
index 0eb95a18f..9188ae9fb 100644
--- a/src/Server.c
+++ b/src/Server.c
@@ -296,7 +296,6 @@ static void MPConnection_BeginConnect(void) {
 	String_InitArray(title, titleBuffer);
 
 	/* Default block permissions (in case server supports SetBlockPermissions but doesn't send) */
-	Blocks.CanPlace[BLOCK_AIR] = false;         Blocks.CanDelete[BLOCK_AIR] = false;
 	Blocks.CanPlace[BLOCK_LAVA] = false;        Blocks.CanDelete[BLOCK_LAVA] = false;
 	Blocks.CanPlace[BLOCK_WATER] = false;       Blocks.CanDelete[BLOCK_WATER] = false;
 	Blocks.CanPlace[BLOCK_STILL_LAVA] = false;  Blocks.CanDelete[BLOCK_STILL_LAVA] = false;