diff --git a/src/normalized.jl b/src/normalized.jl
index 9454311..623a3fc 100644
--- a/src/normalized.jl
+++ b/src/normalized.jl
@@ -19,8 +19,8 @@ function evaluate{T <: Union{Hamming, Levenshtein, DamerauLevenshtein}}(
     return distance / len2
 end
 
-function evaluate(normalized::Normalized{QGram}, s1::AbstractString, s2::AbstractString, 
+function evaluate{T <: QGram}(normalized::Normalized{T}, s1::AbstractString, s2::AbstractString, 
     len1::Integer, len2::Integer)
     distance = evaluate(normalized.dist, s1, s2, len1, len2)
-    return distance / (len1 + len2 - 2 * normalized.dist.q - 2)
+    return distance / (max(0, len1 - normalized.dist.q + 1) + max(0, len2 - normalized.dist.q + 1))
 end
\ No newline at end of file
diff --git a/test/distances.jl b/test/distances.jl
index 1cd78ea..3d7a2d8 100644
--- a/test/distances.jl
+++ b/test/distances.jl
@@ -51,10 +51,16 @@ using StringDistances, Base.Test
 
 
 
+
+
 @test evaluate(QGram(1), "", "abc") == 3
 @test evaluate(QGram(1), "abc", "cba") == 0
 @test evaluate(QGram(1), "abc", "ccc") == 4
 
+@test_approx_eq_eps evaluate(Normalized(QGram(1)), "", "abc") 1.0 1e-4
+@test_approx_eq_eps evaluate(Normalized(QGram(1)), "abc", "cba") 0.0 1e-4
+@test_approx_eq_eps evaluate(Normalized(QGram(1)), "abc", "ccc") 2/3 1e-4
+
 
 @test_approx_eq_eps evaluate(Jaccard(1), "", "abc") 1.0 1e-4
 @test_approx_eq_eps evaluate(Jaccard(1), "abc", "ccc") .666666 1e-4