diff --git a/mappings/net/minecraft/util/math/MathUtils.mapping b/mappings/net/minecraft/util/math/MathUtils.mapping
index 3ac0dbb625..84b75bee5f 100644
--- a/mappings/net/minecraft/util/math/MathUtils.mapping
+++ b/mappings/net/minecraft/util/math/MathUtils.mapping
@@ -138,3 +138,5 @@ CLASS none/or net/minecraft/util/math/MathUtils
 		ARG 0 value
 	METHOD h getFractionalPart (D)D
 		ARG 0 value
+	METHOD i fastInverseSqrt (D)D
+		ARG 0 value