diff --git a/doc/forum/git-annex_6.20170520_doesn__39__t_build_with_QuickCheck_2.10.mdwn b/doc/forum/git-annex_6.20170520_doesn__39__t_build_with_QuickCheck_2.10.mdwn
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+    [  9 of 561] Compiling Utility.QuickCheck ( Utility/QuickCheck.hs, dist/build/git-annex/git-annex-tmp/Utility/QuickCheck.dyn_o )
+    
+    Utility/QuickCheck.hs:38:10: error:
+        Duplicate instance declarations:
+          instance Arbitrary EpochTime
+            -- Defined at Utility/QuickCheck.hs:38:10
+          instance [safe] Arbitrary Foreign.C.Types.CTime
+            -- Defined in ‘Test.QuickCheck.Arbitrary’