diff --git a/library/init/reserved_notation.lean b/library/init/reserved_notation.lean
index c511cb0e63..010ab1c9b6 100644
--- a/library/init/reserved_notation.lean
+++ b/library/init/reserved_notation.lean
@@ -46,6 +46,7 @@ reserve infix `=`:50
 reserve infix `≠`:50
 reserve infix `≈`:50
 reserve infix `∼`:50
+reserve infix `≡`:50
 
 reserve infixr `∘`:60                   -- input with \comp
 reserve postfix `⁻¹`:std.prec.max_plus  -- input with \sy or \-1 or \inv