diff --git a/common/src/main/kotlin/quaedam/shell/network/ServerboundPSHLockAcquirePacket.kt b/common/src/main/kotlin/quaedam/shell/network/ServerboundPSHLockAcquirePacket.kt
index 39f9147..d394a44 100644
--- a/common/src/main/kotlin/quaedam/shell/network/ServerboundPSHLockAcquirePacket.kt
+++ b/common/src/main/kotlin/quaedam/shell/network/ServerboundPSHLockAcquirePacket.kt
@@ -6,6 +6,7 @@ import net.minecraft.network.FriendlyByteBuf
 import net.minecraft.server.level.ServerLevel
 import net.minecraft.server.level.ServerPlayer
 import quaedam.shell.ProjectionShell
+import quaedam.shell.ProjectionShellBlock
 import quaedam.shell.ProjectionShellMutex
 import java.util.function.Supplier
 
@@ -33,7 +34,12 @@ data class ServerboundPSHLockAcquirePacket(val pos: BlockPos) {
         if (!ctx.player.level().isClientSide) {
             ctx.queue {
                 val player = ctx.player as ServerPlayer
-                val result = ProjectionShellMutex.tryLock(ctx.player.level() as ServerLevel, pos, player)
+                val level = ctx.player.level() as ServerLevel
+                if (level.getBlockState(pos).block !is ProjectionShellBlock) {
+                    ProjectionShell.channel.sendToPlayer(player, ClientboundPSHLockResultPacket(pos, false))
+                    return@queue
+                }
+                val result = ProjectionShellMutex.tryLock(level, pos, player)
                 ProjectionShell.channel.sendToPlayer(player, ClientboundPSHLockResultPacket(pos, result))
             }
         }