diff --git a/CHANGES.markdown b/CHANGES.markdown
--- a/CHANGES.markdown
+++ b/CHANGES.markdown
@@ -1,3 +1,9 @@
+* 0.1.2 (5 May 2020)
+
+  Improvements to stability/accuraty of `cubForm` and
+  `quartForm`, contributed by Jasper Van der Jeugt
+  ([#7](https://github.com/diagrams/diagrams-solve/pull/7), [#8](https://github.com/diagrams/diagrams-solve/pull/8))
+
 * 0.1.1 (3 July 2017)
 
   allow base-4.10 for GHC-8.2
diff --git a/diagrams-solve.cabal b/diagrams-solve.cabal
--- a/diagrams-solve.cabal
+++ b/diagrams-solve.cabal
@@ -1,5 +1,5 @@
 name:                diagrams-solve
-version:             0.1.1
+version:             0.1.2
 synopsis:            Pure Haskell solver routines used by diagrams
 description:         Pure Haskell solver routines used by the diagrams
                      project.  Currently includes finding real roots
@@ -15,7 +15,7 @@
 build-type:          Simple
 extra-source-files:  README.markdown, CHANGES.markdown
 cabal-version:       >=1.10
-Tested-with:         GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.1, GHC == 8.2.1
+Tested-with:         GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.3, GHC == 8.6.1, GHC == 8.8.1
 Source-repository head
   type:     git
   location: http://github.com/diagrams/diagrams-solve.git
@@ -23,7 +23,7 @@
 library
   exposed-modules:     Diagrams.Solve.Polynomial,
                        Diagrams.Solve.Tridiagonal
-  build-depends:       base >=4.5 && < 4.11
+  build-depends:       base >=4.5 && < 5.0
   hs-source-dirs:      src
   default-language:    Haskell2010
 
@@ -33,10 +33,9 @@
   -- other-modules: Instances
   hs-source-dirs: tests
   default-language:    Haskell2010
-  build-depends:       base >= 4.2 && < 4.11,
-                       tasty >= 0.10 && < 0.12,
-                       tasty-hunit >= 0.9.2 && < 0.10,
-                       tasty-quickcheck >= 0.8 && < 0.9,
+  build-depends:       base >= 4.2 && < 5.0,
                        deepseq >= 1.3 && < 1.5,
-                       diagrams-solve
-
+                       diagrams-solve,
+                       tasty >= 0.10 && < 1.3,
+                       tasty-hunit >= 0.9.2 && < 0.11,
+                       tasty-quickcheck >= 0.8 && < 0.11
diff --git a/src/Diagrams/Solve/Polynomial.hs b/src/Diagrams/Solve/Polynomial.hs
--- a/src/Diagrams/Solve/Polynomial.hs
+++ b/src/Diagrams/Solve/Polynomial.hs
@@ -107,8 +107,7 @@
  where delta  = 18*a*b*c*d - 4*b^3*d + b^2*c^2 - 4*a*c^3 - 27*a^2*d^2
        disc   = 3*a*c - b^2
        qq     = sqrt(-27*(a^2)*delta)
-       qq'    | aboutZero' toler disc = maximumBy (comparing (abs . (+xx))) [qq, -qq]
-              | otherwise = qq
+       qq'    = if abs (xx + qq) > abs (xx - qq) then qq else -qq
        cc     = cubert (1/2*(qq' + xx))
        xx     = 2*b^3 - 9*a*b*c + 27*a^2*d
        p      = disc/(3*a^2)
@@ -169,7 +168,7 @@
       -- | roots of the reduced quartic
       roots | aboutZero' toler r =
                 0 : cubForm 1 0 p q   -- no constant term: y(y^3 + py + q) = 0
-            | u < 0 || v < 0 = []     -- no real solutions due to square root
+            | u < -toler || v < -toler = []     -- no real solutions due to square root
             | otherwise      = s1++s2 -- solutions of the quadratics
 
       -- solve the resolvent cubic - only one solution is needed
diff --git a/tests/Test.hs b/tests/Test.hs
--- a/tests/Test.hs
+++ b/tests/Test.hs
@@ -1,5 +1,6 @@
 module Main where
 
+import Data.List (sort)
 import Diagrams.Solve.Polynomial
 
 import Test.Tasty (defaultMain, testGroup, TestTree)
@@ -12,6 +13,17 @@
 -- could verify number of solutions, but we would just duplicate the function definition
         , testProperty "solutions found satisfy cubic equation" $
          \a b c d -> let sat x =  a * x * x * x + b * x * x + c * x + d =~ (0 :: Double) in all sat (cubForm a b c d)
+
+-- some specific examples and regression tests
+        , testGroup "Solve specific examples" [
+            testProperty "1 * x^3 + -886.7970773009183 * x^2 + 262148.4783430062 * x + -264000817.775054 = 0" $
+                let [r] = cubForm 1 (-886.7970773009183) 262148.4783430062 (-264000817.775054) in
+                r =~ 915.4538593912
+
+          , testProperty "1 * u^4 + -240 * u^3 + 25449 * u^2 + -1325880 * u + 26471900.25 = 0" $
+                let [r1, r2] = sort $ quartForm 1 (-240) 25449 (-1325880) 26471900.25 in
+                r1 =~ 50.6451 && r2 =~ 69.3549
+            ]
         ]
 
 (=~) :: Double -> Double -> Bool