diff --git a/src/disambiguities.jl b/src/disambiguities.jl
index 7d822b91..6387ca83 100644
--- a/src/disambiguities.jl
+++ b/src/disambiguities.jl
@@ -1,9 +1,17 @@
-for op in (:isless, :(==), :isequal, :(<)), (type, _, _) in ABSTRACT_QUANTITY_TYPES
+for op in (:(==), :(<)), (type, _, _) in ABSTRACT_QUANTITY_TYPES
     @eval begin
         Base.$(op)(::$type, ::Missing) = missing
         Base.$(op)(::Missing, ::$type) = missing
     end
 end
+for (type, _, _) in ABSTRACT_QUANTITY_TYPES
+    @eval begin
+        Base.isequal(::$type, ::Missing) = false
+        Base.isequal(::Missing, ::$type) = false
+        Base.isless(::$type, ::Missing) = true
+        Base.isless(::Missing, ::$type) = false
+    end
+end
 for op in (:isapprox,), (type, _, _) in ABSTRACT_QUANTITY_TYPES
     @eval begin
         Base.$(op)(::$type, ::Missing; kws...) = missing
diff --git a/test/unittests.jl b/test/unittests.jl
index 9f2ee5e5..4fc0c3fc 100644
--- a/test/unittests.jl
+++ b/test/unittests.jl
@@ -1165,8 +1165,8 @@ end
     @test round(Union{Int32,Missing}, FixedRational{Int32,100}(1)) isa Int32
     @test round(Union{Int32,Missing}, FixedRational{Int32,100}(1)) === Int32(1)
     y = missing
-    @test isless(x, y) === missing
-    @test isless(y, x) === missing
+    @test (x < y) === missing
+    @test (y < x) === missing
     @test (x == y) === missing
     @test (y == x) === missing
     @test isapprox(x, y) === missing
@@ -1176,6 +1176,15 @@ end
     y = missing
     @test x * y === missing
     @test x + y === missing
+
+    @testset "$(typeof(q))" for q in (1.0u"m", 1.0us"mg", RealQuantity(1.0u"m"), GenericQuantity(1.0u"m"))
+        @test isequal(q, missing) === false
+        @test isequal(missing, q) === false
+        @test isless(q, missing) === true
+        @test isless(missing, q) === false
+        @test isequal(sort([missing, 2q, q]), [q, 2q, missing])
+        @test findfirst(isequal(missing), [q, missing]) == 2
+    end
 end