diff --git a/Project.toml b/Project.toml
index 5b8f6f1..27eaef8 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "Roots"
 uuid = "f2b01f46-fcfa-551c-844a-d8ac1e96c665"
-version = "2.1.4"
+version = "2.1.5"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
diff --git a/src/utils.jl b/src/utils.jl
index 240b310..f94e305 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -107,7 +107,7 @@ function quad_vertex(c, fc, b, fb, a, fa)
     fba = (fb - fa) / (b - a)
     fbc = (fb - fc) / (b - c)
 
-    1 / 2 * ((a + b) - fba / (fbc - fba) * (c - a))
+    ((a + b) - fba / (fbc - fba) * (c - a)) / 2
 end
 
 ## inverse quadratic
diff --git a/test/test_find_zero.jl b/test/test_find_zero.jl
index ef4e136..28c4d1e 100644
--- a/test/test_find_zero.jl
+++ b/test/test_find_zero.jl
@@ -37,6 +37,7 @@ struct Order3_Test <: Roots.AbstractSecantMethod end
         @test find_zero(sin, big(3), m) ≈ pi
         @test find_zero(sin, big(3.0), m) ≈ pi
         @test find_zero(x -> x^2 - 2.0f0, 2.0f0, m) ≈ sqrt(2) # issue 421
+        @test isnan(solve(ZeroProblem(x -> x^2 + 2, 0.5f0)))
     end
 
     ## defaults for method argument