diff --git a/Cabal/src/Distribution/Simple/Haddock.hs b/Cabal/src/Distribution/Simple/Haddock.hs
index 784894325cb..f06824b24a9 100644
--- a/Cabal/src/Distribution/Simple/Haddock.hs
+++ b/Cabal/src/Distribution/Simple/Haddock.hs
@@ -821,6 +821,13 @@ renderArgs verbosity tmpFileOpts version comp platform args k = do
         else k (renderedArgs, result)
   where
     outputDir = (unDir $ argOutputDir args)
+    isNotArgContents = isNothing (flagToMaybe $ argContents args)
+    isNotArgIndex = isNothing (flagToMaybe $ argIndex args)
+    isArgGenIndex = fromFlagOrDefault False (argGenIndex args)
+    -- Haddock, when generating HTML, does not generate an index if the options
+    -- --use-contents or --use-index are passed to it. See
+    -- https://haskell-haddock.readthedocs.io/en/latest/invoking.html#cmdoption-use-contents
+    isIndexGenerated = isArgGenIndex && isNotArgContents && isNotArgIndex
     result =
       intercalate ", "
         . map
@@ -828,7 +835,7 @@ renderArgs verbosity tmpFileOpts version comp platform args k = do
               outputDir
                 </> case o of
                   Html
-                    | fromFlagOrDefault False (argGenIndex args) ->
+                    | isIndexGenerated ->
                         "index.html"
                   Html
                     | otherwise ->
diff --git a/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.cabal b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.cabal
new file mode 100644
index 00000000000..6808223d511
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.cabal
@@ -0,0 +1,10 @@
+cabal-version: 3.6
+name:          A
+synopsis:      A minimal test package for testing haddock.
+version:       0.0.0
+
+library
+  build-depends:    base
+  default-language: Haskell2010
+  exposed-modules:  A
+  hs-source-dirs:   .
diff --git a/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.hs b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.hs
new file mode 100644
index 00000000000..d34efe10291
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/A/A.hs
@@ -0,0 +1,6 @@
+-- | A minimal test module for testing haddock.
+module A (a) where
+
+-- | a is zero.
+a :: Int
+a = 0
diff --git a/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.out b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.out
new file mode 100644
index 00000000000..e17593a966c
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.out
@@ -0,0 +1,10 @@
+# cabal haddock
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - A-0.0.0 (lib) (first run)
+Configuring library for A-0.0.0...
+Preprocessing library for A-0.0.0...
+Running Haddock on library for A-0.0.0...
+Documentation created: <ROOT>/cabal.dist/work/dist/build/<ARCH>/ghc-<GHCVER>/A-0.0.0/doc/html/A-0.0.0-docs/, <ROOT>/cabal.dist/work/dist/build/<ARCH>/ghc-<GHCVER>/A-0.0.0/doc/html/A-0.0.0-docs/A.txt
+Documentation tarball created: <ROOT>/cabal.dist/work/./dist/A-0.0.0-docs.tar.gz
diff --git a/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.project b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.project
new file mode 100644
index 00000000000..421457f944c
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.project
@@ -0,0 +1 @@
+packages: A
diff --git a/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.test.hs b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.test.hs
new file mode 100644
index 00000000000..00fcfe4b28e
--- /dev/null
+++ b/cabal-testsuite/PackageTests/NewHaddock/HaddockOutput/HaddockForHackageCmdOutput/cabal.test.hs
@@ -0,0 +1,7 @@
+import Test.Cabal.Prelude
+
+-- Test that `cabal haddock --haddock-for-hackage` does not report that it
+-- creates an `index.html` file.
+main = cabalTest $ do
+  r <- cabal' "haddock" ["--haddock-for-hackage", "A"]
+  assertOutputDoesNotContain "index.html" r
diff --git a/changelog.d/pr-9332 b/changelog.d/pr-9332
new file mode 100644
index 00000000000..c5d4c3d4ac4
--- /dev/null
+++ b/changelog.d/pr-9332
@@ -0,0 +1,4 @@
+synopsis: Don't report `index.html` file as created, if not created by Haddock
+packages: Cabal cabal-install
+prs: #9332
+issues: #5120