diff --git a/src/interface/quadratization.jl b/src/interface/quadratization.jl
index 5bc486b..6757472 100644
--- a/src/interface/quadratization.jl
+++ b/src/interface/quadratization.jl
@@ -17,7 +17,7 @@ end
 @doc raw"""
     infer_quadratization(f::AbstractPBF)
 
-For a given PBF, returns whether it should be quadratized or not, based on its degree.
+For a given PBF, returns whether it should be quadratized or not, based on its characteristics.
 """
 function infer_quadratization end
 
diff --git a/src/library/variables/varlt.jl b/src/library/variables/varlt.jl
index 6ddd5f3..84c5fbb 100644
--- a/src/library/variables/varlt.jl
+++ b/src/library/variables/varlt.jl
@@ -6,6 +6,8 @@ function varlt(u::V, v::V) where {V<:Signed}
     # 0, 1, 2, 3, ..., -1, -2, -3, ...
     if sign(u) == sign(v)
         return isless(abs(u), abs(v))
+    elseif sign(u) >= 0 && sign(v) >= 0
+        return isless(sign(u), sign(v))
     else
         return isless(sign(v), sign(u))
     end
diff --git a/test/unit/variables.jl b/test/unit/variables.jl
index 6aa0d59..56ef695 100644
--- a/test/unit/variables.jl
+++ b/test/unit/variables.jl
@@ -11,10 +11,18 @@ function test_variable_system()
             end
 
             @testset "∴ Integer" begin
-                @test PBO.varlt(1, 1) === false
+                @test PBO.varlt(0, 1) === true
+                @test PBO.varlt(1, 0) === false
+                
+                @test PBO.varlt(0, -1) === true
+                @test PBO.varlt(-1, 0) === false
+
                 @test PBO.varlt(1, 2) === true
                 @test PBO.varlt(2, 1) === false
 
+                @test PBO.varlt(0, 0) === false
+                @test PBO.varlt(1, 1) === false
+
                 @test PBO.varlt(1, -1) === true
                 @test PBO.varlt(-1, 1) === false