diff --git a/core/src/main/java/nl/matsv/viabackwards/api/data/VBMappingDataLoader.java b/core/src/main/java/nl/matsv/viabackwards/api/data/VBMappingDataLoader.java
index fdd8830b..520645a3 100644
--- a/core/src/main/java/nl/matsv/viabackwards/api/data/VBMappingDataLoader.java
+++ b/core/src/main/java/nl/matsv/viabackwards/api/data/VBMappingDataLoader.java
@@ -67,9 +67,10 @@ public class VBMappingDataLoader {
                     String diffValue = diffValueJson != null ? diffValueJson.getAsString() : null;
 
                     int dataIndex;
-                    if (diffValue == null && (dataIndex = key.indexOf('[')) != -1) {
+                    if (diffValue == null && (dataIndex = key.indexOf('[')) != -1
+                            && (diffValueJson = diffIdentifiers.getAsJsonPrimitive(key.substring(0, dataIndex))) != null) {
                         // Check for wildcard mappings
-                        diffValue = diffIdentifiers.getAsJsonPrimitive(key.substring(0, dataIndex)).getAsString();
+                        diffValue = diffValueJson.getAsString();
 
                         // Keep original properties if value ends with [
                         if (diffValue.endsWith("[")) {
diff --git a/core/src/main/resources/assets/viabackwards/data/mapping-1.13.2to1.14.json b/core/src/main/resources/assets/viabackwards/data/mapping-1.13.2to1.14.json
index f20b98b8..2b185700 100644
--- a/core/src/main/resources/assets/viabackwards/data/mapping-1.13.2to1.14.json
+++ b/core/src/main/resources/assets/viabackwards/data/mapping-1.13.2to1.14.json
@@ -350,7 +350,8 @@
     "minecraft:polished_andesite_slab": "minecraft:stone_brick_slab[",
     "minecraft:diorite_slab": "minecraft:quartz_slab[",
     "minecraft:brick_wall": "minecraft:cobblestone_wall[",
-    "minecraft:prismarine_wall": "minecraft:cobblestone_wall[", 
+    "minecraft:prismarine_wall": "minecraft:cobblestone_wall[",
+    "minecraft:sandstone_wall": "minecraft:cobblestone_wall[",
     "minecraft:red_sandstone_wall": "minecraft:cobblestone_wall[", 
     "minecraft:mossy_stone_brick_wall": "minecraft:mossy_cobblestone_wall[",
     "minecraft:granite_wall": "minecraft:cobblestone_wall[",