diff --git a/api/src/main/java/com/viaversion/viaversion/api/protocol/version/ProtocolVersion.java b/api/src/main/java/com/viaversion/viaversion/api/protocol/version/ProtocolVersion.java
index 247feb6c8..da3b6f14e 100644
--- a/api/src/main/java/com/viaversion/viaversion/api/protocol/version/ProtocolVersion.java
+++ b/api/src/main/java/com/viaversion/viaversion/api/protocol/version/ProtocolVersion.java
@@ -76,7 +76,7 @@ public class ProtocolVersion {
     public static final ProtocolVersion v1_16_2 = register(751, "1.16.2");
     public static final ProtocolVersion v1_16_3 = register(753, "1.16.3");
     public static final ProtocolVersion v1_16_4 = register(754, "1.16.4/5", new VersionRange("1.16", 4, 5));
-    public static final ProtocolVersion v1_17 = register(755, 25, "1.17");
+    public static final ProtocolVersion v1_17 = register(755, 26, "1.17");
     public static final ProtocolVersion unknown = register(-1, "UNKNOWN");
 
     public static ProtocolVersion register(int version, String name) {
diff --git a/build.gradle.kts b/build.gradle.kts
index aea487fe0..f0c9c1786 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -8,7 +8,7 @@ plugins {
 
 allprojects {
     group = "com.viaversion"
-    version = "4.0.0-21w17a"
+    version = "4.0.0-21w18a"
     description = "Allow newer clients to join older server versions."
 }
 
diff --git a/common/src/main/resources/assets/viaversion/data/mapping-1.17.json b/common/src/main/resources/assets/viaversion/data/mapping-1.17.json
index 0a2b96f3a..226230742 100644
--- a/common/src/main/resources/assets/viaversion/data/mapping-1.17.json
+++ b/common/src/main/resources/assets/viaversion/data/mapping-1.17.json
@@ -21777,8 +21777,8 @@
     "534": "minecraft:diorite_stairs",
     "535": "minecraft:cobbled_deepslate_stairs",
     "536": "minecraft:polished_deepslate_stairs",
-    "537": "minecraft:deepslate_tile_stairs",
-    "538": "minecraft:deepslate_brick_stairs",
+    "537": "minecraft:deepslate_brick_stairs",
+    "538": "minecraft:deepslate_tile_stairs",
     "539": "minecraft:polished_granite_slab",
     "540": "minecraft:smooth_red_sandstone_slab",
     "541": "minecraft:mossy_stone_brick_slab",