diff --git a/cabal-install/Distribution/Solver/Modular/Index.hs b/cabal-install/Distribution/Solver/Modular/Index.hs
index c1a8c0be412..2f28d12de85 100644
--- a/cabal-install/Distribution/Solver/Modular/Index.hs
+++ b/cabal-install/Distribution/Solver/Modular/Index.hs
@@ -42,14 +42,15 @@ data ComponentInfo = ComponentInfo {
     compIsVisible   :: IsVisible
   , compIsBuildable :: IsBuildable
   }
+  deriving Show
 
 -- | Whether a component is visible in the current environment.
 newtype IsVisible = IsVisible Bool
-  deriving Eq
+  deriving (Eq, Show)
 
 -- | Whether a component is made unbuildable by a "buildable: False" field.
 newtype IsBuildable = IsBuildable Bool
-  deriving Eq
+  deriving (Eq, Show)
 
 mkIndex :: [(PN, I, PInfo)] -> Index
 mkIndex xs = M.map M.fromList (groupMap (L.map (\ (pn, i, pi) -> (pn, (i, pi))) xs))
diff --git a/cabal-install/Distribution/Solver/Modular/Validate.hs b/cabal-install/Distribution/Solver/Modular/Validate.hs
index 9c20c9bc321..b809e4fbbda 100644
--- a/cabal-install/Distribution/Solver/Modular/Validate.hs
+++ b/cabal-install/Distribution/Solver/Modular/Validate.hs
@@ -230,7 +230,7 @@ validate = cata go
           let newDeps :: Either Conflict (PPreAssignment, Map QPN ComponentDependencyReasons)
               newDeps = do
                 nppa <- mnppa
-                rComps' <- extendRequiredComponents aComps rComps newactives
+                rComps' <- extendRequiredComponents qpn aComps rComps newactives
                 checkComponentsInNewPackage (M.findWithDefault M.empty qpn rComps) qpn comps
                 return (nppa, rComps')
           in case newDeps of
@@ -265,7 +265,7 @@ validate = cata go
       -- We now try to get the new active dependencies we might learn about because
       -- we have chosen a new flag.
       let newactives = extractNewDeps (F qfn) b npfa psa qdeps
-          mNewRequiredComps = extendRequiredComponents aComps rComps newactives
+          mNewRequiredComps = extendRequiredComponents qpn aComps rComps newactives
       -- As in the package case, we try to extend the partial assignment.
       let mnppa = extend extSupported langSupported pkgPresent newactives ppa
       case liftM2 (,) mnppa mNewRequiredComps of
@@ -295,7 +295,7 @@ validate = cata go
       -- We now try to get the new active dependencies we might learn about because
       -- we have chosen a new flag.
       let newactives = extractNewDeps (S qsn) b pfa npsa qdeps
-          mNewRequiredComps = extendRequiredComponents aComps rComps newactives
+          mNewRequiredComps = extendRequiredComponents qpn aComps rComps newactives
       -- As in the package case, we try to extend the partial assignment.
       let mnppa = extend extSupported langSupported pkgPresent newactives ppa
       case liftM2 (,) mnppa mNewRequiredComps of
@@ -534,11 +534,12 @@ createConflictSetForVersionConflict pkg
 -- known component dependencies. It returns a failure when a new dependency
 -- requires a component that is missing, private, or unbuildable in a previously
 -- chosen package.
-extendRequiredComponents :: Map QPN (Map ExposedComponent ComponentInfo)
+extendRequiredComponents :: QPN -- ^ package we extend
+                         -> Map QPN (Map ExposedComponent ComponentInfo)
                          -> Map QPN ComponentDependencyReasons
                          -> [LDep QPN]
                          -> Either Conflict (Map QPN ComponentDependencyReasons)
-extendRequiredComponents available = foldM extendSingle
+extendRequiredComponents eqpn available = foldM extendSingle
   where
     extendSingle :: Map QPN ComponentDependencyReasons
                  -> LDep QPN
@@ -554,7 +555,9 @@ extendRequiredComponents available = foldM extendSingle
                  Nothing ->
                      Left $ mkConflict qpn comp dr PackageRequiresMissingComponent
                  Just compInfo
-                   | compIsVisible compInfo == IsVisible False ->
+                   | compIsVisible compInfo == IsVisible False
+                   , eqpn /= qpn -- package components can depend on other components
+                   ->
                      Left $ mkConflict qpn comp dr PackageRequiresPrivateComponent
                    | compIsBuildable compInfo == IsBuildable False ->
                      Left $ mkConflict qpn comp dr PackageRequiresUnbuildableComponent
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.out b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.out
new file mode 100644
index 00000000000..a063ee92cb8
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.out
@@ -0,0 +1,7 @@
+# cabal v2-build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following would be built:
+ - pkg-foo-0 (lib:internal-lib) (first run)
+ - pkg-foo-0 (lib) (first run)
+ - pkg-bar-0 (exe:example) (first run)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.project b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.project
new file mode 100644
index 00000000000..56221084a1f
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.project
@@ -0,0 +1 @@
+packages: pkg-foo pkg-bar
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.test.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.test.hs
new file mode 100644
index 00000000000..915337859f5
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/cabal.test.hs
@@ -0,0 +1,3 @@
+import Test.Cabal.Prelude
+main = cabalTest $
+  cabal "v2-build" ["all", "--dry-run", "--enable-tests"]
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/exe/Main.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/exe/Main.hs
new file mode 100644
index 00000000000..5edf24437d0
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/exe/Main.hs
@@ -0,0 +1,6 @@
+module Main where
+
+import Lib
+
+main :: IO ()
+main = print value
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/pkg-bar.cabal b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/pkg-bar.cabal
new file mode 100644
index 00000000000..a8c855e8fbc
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-bar/pkg-bar.cabal
@@ -0,0 +1,13 @@
+cabal-version: 2.0
+name: pkg-bar
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+executable example
+  default-language: Haskell2010
+  hs-source-dirs: exe
+  main-is: Main.hs
+  build-depends: base, pkg-foo
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/internal/InternalLib.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/internal/InternalLib.hs
new file mode 100644
index 00000000000..b925bcad362
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/internal/InternalLib.hs
@@ -0,0 +1,4 @@
+module InternalLib where
+
+value :: Int
+value = 42
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/pkg-foo.cabal b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/pkg-foo.cabal
new file mode 100644
index 00000000000..d22f7a32a6b
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/pkg-foo.cabal
@@ -0,0 +1,19 @@
+cabal-version: 2.0
+name: pkg-foo
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+library
+  default-language: Haskell2010
+  hs-source-dirs: src
+  build-depends: base <5, internal-lib
+  exposed-modules: Lib
+
+library internal-lib
+  default-language: Haskell2010
+  hs-source-dirs: internal
+  build-depends: base <5
+  exposed-modules: InternalLib
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/src/Lib.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/src/Lib.hs
new file mode 100644
index 00000000000..c7683f97b49
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepExternal/pkg-foo/src/Lib.hs
@@ -0,0 +1,3 @@
+module Lib (value) where
+
+import InternalLib (value)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.out b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.out
new file mode 100644
index 00000000000..aa10de2a405
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.out
@@ -0,0 +1,8 @@
+# cabal v2-build
+Resolving dependencies...
+cabal: Could not resolve dependencies:
+[__0] trying: pkg-bar-0 (user goal)
+[__1] next goal: pkg-foo (user goal)
+[__1] rejecting: pkg-foo-0 (library 'internal-lib' is private, but it is required by pkg-bar)
+[__1] fail (backjumping, conflict set: pkg-bar, pkg-foo)
+After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: pkg-bar (2), pkg-foo (2)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.project b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.project
new file mode 100644
index 00000000000..56221084a1f
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.project
@@ -0,0 +1 @@
+packages: pkg-foo pkg-bar
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.test.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.test.hs
new file mode 100644
index 00000000000..6b4ad601b07
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/cabal.test.hs
@@ -0,0 +1,5 @@
+import Test.Cabal.Prelude
+main = cabalTest $
+  -- we try to depend on private component from outside,
+  -- so this should fail.
+  fails $ cabal "v2-build" ["all", "--dry-run", "--enable-tests"]
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/exe/Main.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/exe/Main.hs
new file mode 100644
index 00000000000..cfae2b73f2a
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/exe/Main.hs
@@ -0,0 +1,6 @@
+module Main where
+
+import InternalLib
+
+main :: IO ()
+main = print value
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/pkg-bar.cabal b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/pkg-bar.cabal
new file mode 100644
index 00000000000..2895fd54b2c
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-bar/pkg-bar.cabal
@@ -0,0 +1,13 @@
+cabal-version: 3.0
+name: pkg-bar
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+executable example
+  default-language: Haskell2010
+  hs-source-dirs: exe
+  main-is: Main.hs
+  build-depends: base, pkg-foo:internal-lib
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/internal/InternalLib.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/internal/InternalLib.hs
new file mode 100644
index 00000000000..b925bcad362
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/internal/InternalLib.hs
@@ -0,0 +1,4 @@
+module InternalLib where
+
+value :: Int
+value = 42
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/pkg-foo.cabal b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/pkg-foo.cabal
new file mode 100644
index 00000000000..d22f7a32a6b
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/pkg-foo.cabal
@@ -0,0 +1,19 @@
+cabal-version: 2.0
+name: pkg-foo
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+library
+  default-language: Haskell2010
+  hs-source-dirs: src
+  build-depends: base <5, internal-lib
+  exposed-modules: Lib
+
+library internal-lib
+  default-language: Haskell2010
+  hs-source-dirs: internal
+  build-depends: base <5
+  exposed-modules: InternalLib
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/src/Lib.hs b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/src/Lib.hs
new file mode 100644
index 00000000000..c7683f97b49
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/DepInternal/pkg-foo/src/Lib.hs
@@ -0,0 +1,3 @@
+module Lib (value) where
+
+import InternalLib (value)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.out b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.out
new file mode 100644
index 00000000000..bde31817cf4
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.out
@@ -0,0 +1,6 @@
+# cabal v2-build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following would be built:
+ - issue6961-0 (lib:internal-lib) (first run)
+ - issue6961-0 (exe:example) (first run)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.project b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.project
new file mode 100644
index 00000000000..e6fdbadb439
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.project
@@ -0,0 +1 @@
+packages: .
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.test.hs b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.test.hs
new file mode 100644
index 00000000000..915337859f5
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/cabal.test.hs
@@ -0,0 +1,3 @@
+import Test.Cabal.Prelude
+main = cabalTest $
+  cabal "v2-build" ["all", "--dry-run", "--enable-tests"]
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/exe/Main.hs b/cabal-testsuite/PackageTests/Regression/T6961/Exe/exe/Main.hs
new file mode 100644
index 00000000000..5edf24437d0
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/exe/Main.hs
@@ -0,0 +1,6 @@
+module Main where
+
+import Lib
+
+main :: IO ()
+main = print value
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/issue6961.cabal b/cabal-testsuite/PackageTests/Regression/T6961/Exe/issue6961.cabal
new file mode 100644
index 00000000000..c2e3faf69f1
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/issue6961.cabal
@@ -0,0 +1,19 @@
+cabal-version: 2.0
+name: issue6961
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+library internal-lib
+  default-language: Haskell2010
+  hs-source-dirs: src
+  build-depends: base <5
+  exposed-modules: Lib
+
+executable example
+  default-language: Haskell2010
+  hs-source-dirs: exe
+  main-is: Main.hs
+  build-depends: base, internal-lib
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Exe/src/Lib.hs b/cabal-testsuite/PackageTests/Regression/T6961/Exe/src/Lib.hs
new file mode 100644
index 00000000000..e4dce2beed1
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Exe/src/Lib.hs
@@ -0,0 +1,4 @@
+module Lib where
+
+value :: Int
+value = 42
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.out b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.out
new file mode 100644
index 00000000000..8f28d66058a
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.out
@@ -0,0 +1,6 @@
+# cabal v2-build
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following would be built:
+ - issue6961-0 (lib:internal-lib) (first run)
+ - issue6961-0 (test:example) (first run)
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.project b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.project
new file mode 100644
index 00000000000..e6fdbadb439
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.project
@@ -0,0 +1 @@
+packages: .
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.test.hs b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.test.hs
new file mode 100644
index 00000000000..915337859f5
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/cabal.test.hs
@@ -0,0 +1,3 @@
+import Test.Cabal.Prelude
+main = cabalTest $
+  cabal "v2-build" ["all", "--dry-run", "--enable-tests"]
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/issue6961.cabal b/cabal-testsuite/PackageTests/Regression/T6961/Test/issue6961.cabal
new file mode 100644
index 00000000000..490ec5f55f9
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/issue6961.cabal
@@ -0,0 +1,20 @@
+cabal-version: 2.0
+name: issue6961
+version: 0
+build-type: Simple
+
+synopsis: This should work
+category: Test
+
+library internal-lib
+  default-language: Haskell2010
+  hs-source-dirs: src
+  build-depends: base <5
+  exposed-modules: Lib
+
+test-suite example
+  type: exitcode-stdio-1.0
+  default-language: Haskell2010
+  hs-source-dirs: tests
+  main-is: Main.hs
+  build-depends: base, internal-lib
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/src/Lib.hs b/cabal-testsuite/PackageTests/Regression/T6961/Test/src/Lib.hs
new file mode 100644
index 00000000000..e4dce2beed1
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/src/Lib.hs
@@ -0,0 +1,4 @@
+module Lib where
+
+value :: Int
+value = 42
diff --git a/cabal-testsuite/PackageTests/Regression/T6961/Test/tests/Main.hs b/cabal-testsuite/PackageTests/Regression/T6961/Test/tests/Main.hs
new file mode 100644
index 00000000000..5edf24437d0
--- /dev/null
+++ b/cabal-testsuite/PackageTests/Regression/T6961/Test/tests/Main.hs
@@ -0,0 +1,6 @@
+module Main where
+
+import Lib
+
+main :: IO ()
+main = print value