diff --git a/ghcide/src/Development/IDE/Core/PluginUtils.hs b/ghcide/src/Development/IDE/Core/PluginUtils.hs
index 330468affe..4f3c88f2e0 100644
--- a/ghcide/src/Development/IDE/Core/PluginUtils.hs
+++ b/ghcide/src/Development/IDE/Core/PluginUtils.hs
@@ -215,10 +215,13 @@ activeDiagnosticsInRangeMT ide nfp range = do
         case mDiags of
             Nothing -> pure Nothing
             Just fileDiags -> do
-                pure $ Just $ filter diagRangeOverlaps fileDiags
+                pure $ Just $ filter (diagRangeOverlaps range) fileDiags
     where
-        diagRangeOverlaps = \fileDiag ->
-            rangesOverlap range (fileDiag ^. fdLspDiagnosticL . LSP.range)
+        -- TODO: document this
+        diagRangeOverlaps range@(LSP.Range b e) fileDiag
+          | b /= e = rangesOverlap range diagRange
+          | otherwise = LSP.positionInRange b diagRange || b == diagEnd
+          where diagRange@(LSP.Range _ diagEnd) = fileDiag ^. fdLspDiagnosticL . LSP.range
 
 -- | Just like 'activeDiagnosticsInRangeMT'. See the docs of 'activeDiagnosticsInRangeMT' for details.
 activeDiagnosticsInRange :: MonadIO m => Shake.ShakeExtras -> NormalizedFilePath -> LSP.Range -> m [FileDiagnostic]
diff --git a/hls-plugin-api/src/Ide/PluginUtils.hs b/hls-plugin-api/src/Ide/PluginUtils.hs
index e34d19f8b0..69f2bdb793 100644
--- a/hls-plugin-api/src/Ide/PluginUtils.hs
+++ b/hls-plugin-api/src/Ide/PluginUtils.hs
@@ -279,8 +279,11 @@ subRange :: Range -> Range -> Bool
 subRange = isSubrangeOf
 
 
--- | Check whether the two 'Range's overlap in any way.
+-- | Check whether the two 'Range's overlap in any way, taking into account
+-- that, as per the LSP spec, 'Range's are right-open half-open intervals.
 --
+-- >>> rangesOverlap (mkRange 1 0 1 2) (mkRange 1 4 1 6)
+-- False
 -- >>> rangesOverlap (mkRange 1 0 1 4) (mkRange 1 2 1 5)
 -- True
 -- >>> rangesOverlap (mkRange 1 2 1 5) (mkRange 1 0 1 4)
@@ -289,9 +292,11 @@ subRange = isSubrangeOf
 -- True
 -- >>> rangesOverlap (mkRange 1 2 1 4) (mkRange 1 0 1 6)
 -- True
+-- >>> rangesOverlap (mkRange 1 2 1 4) (mkRange 1 4 1 6)
+-- False
 rangesOverlap :: Range -> Range -> Bool
 rangesOverlap r1 r2 =
-  r1 ^. L.start <= r2 ^. L.end && r2 ^. L.start <= r1 ^. L.end
+  r1 ^. L.start < r2 ^. L.end && r2 ^. L.start < r1 ^. L.end
 
 -- ---------------------------------------------------------------------
 
diff --git a/plugins/hls-refactor-plugin/test/Main.hs b/plugins/hls-refactor-plugin/test/Main.hs
index 0897b1ca03..8d6ef15f0c 100644
--- a/plugins/hls-refactor-plugin/test/Main.hs
+++ b/plugins/hls-refactor-plugin/test/Main.hs
@@ -1290,7 +1290,7 @@ extendImportTests = testGroup "extend import actions"
                     , "b :: A"
                     , "b = 0"
                     ])
-            (Range (Position 2 5) (Position 2 5))
+            (Range (Position 2 5) (Position 2 6))
             ["Add A to the import list of ModuleA"]
             (T.unlines
                     [ "module ModuleB where"
@@ -2958,7 +2958,7 @@ fillTypedHoleTests = let
               ]
       doc <- createDoc "Test.hs" "haskell" $ mkDoc "_"
       _ <- waitForDiagnostics
-      actions <- getCodeActions doc (Range (Position 2 13) (Position 2 14))
+      actions <- getCodeActions doc (Range (Position 2 12) (Position 2 13))
       chosen <- pickActionWithTitle "Replace _ with (<$>)" actions
       executeCodeAction chosen
       modifiedCode <- documentContents doc
@@ -2971,7 +2971,7 @@ fillTypedHoleTests = let
               ]
       doc <- createDoc "Test.hs" "haskell" $ mkDoc "`_`"
       _ <- waitForDiagnostics
-      actions <- getCodeActions doc (Range (Position 2 16) (Position 2 19))
+      actions <- getCodeActions doc (Range (Position 2 18) (Position 2 19))
       chosen <- pickActionWithTitle "Replace _ with (<$>)" actions
       executeCodeAction chosen
       modifiedCode <- documentContents doc