diff --git a/src/main/java/vazkii/botania/api/lexicon/LexiconRecipeMappings.java b/src/main/java/vazkii/botania/api/lexicon/LexiconRecipeMappings.java
index 49b2a133e..2bb3c1105 100644
--- a/src/main/java/vazkii/botania/api/lexicon/LexiconRecipeMappings.java
+++ b/src/main/java/vazkii/botania/api/lexicon/LexiconRecipeMappings.java
@@ -40,6 +40,9 @@ public final class LexiconRecipeMappings {
 		map(stack, entry, page, false);
 	}
 
+	public static void remove(ItemStack stack) {
+		mappings.remove(stackToString(stack));
+	}
 
 	public static EntryData getDataForStack(ItemStack stack) {
 		return mappings.get(stackToString(stack));
diff --git a/src/main/java/vazkii/botania/api/package-info.java b/src/main/java/vazkii/botania/api/package-info.java
index 4cfcad846..2db13b135 100644
--- a/src/main/java/vazkii/botania/api/package-info.java
+++ b/src/main/java/vazkii/botania/api/package-info.java
@@ -1,4 +1,4 @@
-@API(owner = "Botania", apiVersion = "29", provides = "BotaniaAPI")
+@API(owner = "Botania", apiVersion = "30", provides = "BotaniaAPI")
 package vazkii.botania.api;
 import cpw.mods.fml.common.API;
 
diff --git a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexicon.java b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexicon.java
index f19689616..6979ba37b 100644
--- a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexicon.java
+++ b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexicon.java
@@ -309,4 +309,18 @@ public class GuiLexicon extends GuiScreen {
 		super.keyTyped(par1, par2);
 	}
 
+	public static boolean isValidLexiconGui(GuiLexicon gui)	{
+		if(gui.isCategoryIndex())
+			return true;
+		if(gui.isIndex()) {
+			GuiLexiconIndex indexGui=(GuiLexiconIndex)gui;
+			if(indexGui.category==null)
+				return true;
+			return BotaniaAPI.getAllCategories().contains(indexGui.category);
+		}
+		GuiLexiconEntry entryGui=(GuiLexiconEntry)gui;
+		if(!BotaniaAPI.getAllEntries().contains(entryGui.entry))
+			return false;
+		return entryGui.page < entryGui.entry.pages.size();
+	}
 }
diff --git a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconEntry.java b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconEntry.java
index 43cb3e246..b9262f6cb 100644
--- a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconEntry.java
+++ b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconEntry.java
@@ -59,7 +59,15 @@ public class GuiLexiconEntry extends GuiLexicon implements IGuiLexiconEntry, IPa
 		buttonList.add(rightButton = new GuiButtonPage(2, left + guiWidth - 18, top + guiHeight - 10, true));
 		buttonList.add(shareButton = new GuiButtonShare(3, left + guiWidth - 6, top - 2));
 
+		if(!GuiLexicon.isValidLexiconGui(this))	{
+			currentOpenLexicon = new GuiLexicon();
+			mc.displayGuiScreen(currentOpenLexicon);
+			ClientTickHandler.notifyPageChange();
+			return;
+		}
+		
 		LexiconPage page = entry.pages.get(this.page);
+
 		page.onOpened(this);
 		updatePageButtons();
 	}
diff --git a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconIndex.java b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconIndex.java
index 03b019dd3..6de2deffd 100644
--- a/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconIndex.java
+++ b/src/main/java/vazkii/botania/client/gui/lexicon/GuiLexiconIndex.java
@@ -73,6 +73,14 @@ public class GuiLexiconIndex extends GuiLexicon implements IParented {
 	@Override
 	public void initGui() {
 		super.initGui();
+
+		if(!GuiLexicon.isValidLexiconGui(this))	{
+			currentOpenLexicon = new GuiLexicon();
+			mc.displayGuiScreen(currentOpenLexicon);
+			ClientTickHandler.notifyPageChange();
+			return;
+		}
+
 		buttonList.add(backButton = new GuiButtonBack(12, left + guiWidth / 2 - 8, top + guiHeight + 2));
 		buttonList.add(leftButton = new GuiButtonPage(13, left, top + guiHeight - 10, false));
 		buttonList.add(rightButton = new GuiButtonPage(14, left + guiWidth - 18, top + guiHeight - 10, true));