diff --git a/trees/isa/isa-001M.tree b/trees/isa/isa-001M.tree
index 653d0b3..a415315 100644
--- a/trees/isa/isa-001M.tree
+++ b/trees/isa/isa-001M.tree
@@ -5,7 +5,7 @@
 \parent{isa-001B}
 \taxon{Example}
 \put\shiki/language{Isabelle Theory}
-\shiki{lemma lm001M: ‹f (f (f (b::two))) = f b›}
+\shiki{lemma lm001M: ‹f (f (f (b::oot))) = f b›}
 \solnblock{
 \shiki{apply (case_tac b)
  apply simp
@@ -24,4 +24,4 @@ apply simp
 apply (case_tac "(f TWO)")
  apply simp
 apply simp
-done}}
\ No newline at end of file
+done}}