diff --git a/lib/ruby_units/unit.rb b/lib/ruby_units/unit.rb
index 32d4e188..5b03e66c 100644
--- a/lib/ruby_units/unit.rb
+++ b/lib/ruby_units/unit.rb
@@ -847,7 +847,7 @@ def +(other)
               RubyUnits::Unit.new(scalar: (other.scalar + convert_to(other.temperature_scale).scalar), numerator: other.numerator, denominator: other.denominator, signature: other.signature)
             end
           else
-            RubyUnits::Unit.new(scalar: (base_scalar + other.base_scalar), numerator: base.numerator, denominator: base.denominator, signature: @signature).to(units)
+            RubyUnits::Unit.new(scalar: (base_scalar + other.base_scalar), numerator: base.numerator, denominator: base.denominator, signature: @signature).convert_to(self)
           end
         else
           raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')"
@@ -883,7 +883,7 @@ def -(other)
           elsif other.temperature?
             raise ArgumentError, 'Cannot subtract a temperature from a differential degree unit'
           else
-            RubyUnits::Unit.new(scalar: (base_scalar - other.base_scalar), numerator: base.numerator, denominator: base.denominator, signature: @signature).to(units)
+            RubyUnits::Unit.new(scalar: (base_scalar - other.base_scalar), numerator: base.numerator, denominator: base.denominator, signature: @signature).convert_to(self)
           end
         else
           raise ArgumentError, "Incompatible Units ('#{self}' not compatible with '#{other}')"
diff --git a/spec/ruby_units/unit_spec.rb b/spec/ruby_units/unit_spec.rb
index c02cd766..6ea4805f 100644
--- a/spec/ruby_units/unit_spec.rb
+++ b/spec/ruby_units/unit_spec.rb
@@ -1744,6 +1744,10 @@
       context 'between a degree and a temperature' do
         specify { expect(RubyUnits::Unit.new('100 degK') + RubyUnits::Unit.new('100 tempK')).to eq(RubyUnits::Unit.new('200 tempK')) }
       end
+
+      context 'between two unitless units' do
+        specify { expect(RubyUnits::Unit.new('1') + RubyUnits::Unit.new('2')).to eq 3 }
+      end
     end
 
     context 'subtracting (-)' do
@@ -1784,6 +1788,10 @@
       context 'between a degree and a temperature' do
         specify { expect { (RubyUnits::Unit.new('100 degK') - RubyUnits::Unit.new('100 tempK')) }.to raise_error(ArgumentError, 'Cannot subtract a temperature from a differential degree unit') }
       end
+
+      context 'a unitless unit from another unitless unit' do
+        specify { expect(RubyUnits::Unit.new('1') - RubyUnits::Unit.new('2')).to eq -1 }
+      end
     end
 
     context 'multiplying (*)' do