diff --git a/lib/attrsets.nix b/lib/attrsets.nix
index 31fddc59e20e..812521ce6d1c 100644
--- a/lib/attrsets.nix
+++ b/lib/attrsets.nix
@@ -487,7 +487,7 @@ rec {
        => "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r-dev"
   */
   getOutput = output: pkg:
-    if pkg.outputUnspecified or false
+    if ! pkg ? outputSpecified || ! pkg.outputSpecified
       then pkg.${output} or pkg.out or pkg
       else pkg;
 
diff --git a/lib/customisation.nix b/lib/customisation.nix
index a794b673d70c..234a528527d3 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -145,14 +145,14 @@ rec {
     let
       outputs = drv.outputs or [ "out" ];
 
-      commonAttrs = (removeAttrs drv [ "outputUnspecified" ]) //
-        (builtins.listToAttrs outputsList) //
+      commonAttrs = drv // (builtins.listToAttrs outputsList) //
         ({ all = map (x: x.value) outputsList; }) // passthru;
 
       outputToAttrListElement = outputName:
         { name = outputName;
           value = commonAttrs // {
             inherit (drv.${outputName}) type outputName;
+            outputSpecified = true;
             drvPath = assert condition; drv.${outputName}.drvPath;
             outPath = assert condition; drv.${outputName}.outPath;
           };
@@ -160,7 +160,6 @@ rec {
 
       outputsList = map outputToAttrListElement outputs;
     in commonAttrs // {
-      outputUnspecified = true;
       drvPath = assert condition; drv.drvPath;
       outPath = assert condition; drv.outPath;
     };
diff --git a/pkgs/build-support/buildenv/default.nix b/pkgs/build-support/buildenv/default.nix
index c2186cf6bfa0..006fc2aff923 100644
--- a/pkgs/build-support/buildenv/default.nix
+++ b/pkgs/build-support/buildenv/default.nix
@@ -62,7 +62,7 @@ runCommand name
         # and otherwise use `meta.outputsToInstall`. The attribute is guaranteed
         # to exist in mkDerivation-created cases. The other cases (e.g. runCommand)
         # aren't expected to have multiple outputs.
-        (if drv.outputUnspecified or false
+        (if (! drv ? outputSpecified || ! drv.outputSpecified)
             && drv.meta.outputsToInstall or null != null
           then map (outName: drv.${outName}) drv.meta.outputsToInstall
           else [ drv ])
diff --git a/pkgs/development/compilers/llvm/10/default.nix b/pkgs/development/compilers/llvm/10/default.nix
index 690328b26ae2..8bd7e937e7d7 100644
--- a/pkgs/development/compilers/llvm/10/default.nix
+++ b/pkgs/development/compilers/llvm/10/default.nix
@@ -63,14 +63,14 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     # disabled until recommonmark supports sphinx 3
     #Llvm-manpages = lowPrio (tools.libllvm.override {
diff --git a/pkgs/development/compilers/llvm/11/default.nix b/pkgs/development/compilers/llvm/11/default.nix
index 9834ce30cdd2..ebd0dc672aa3 100644
--- a/pkgs/development/compilers/llvm/11/default.nix
+++ b/pkgs/development/compilers/llvm/11/default.nix
@@ -65,21 +65,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     clang-polly-unwrapped = callPackage ./clang {
       inherit llvm_meta;
diff --git a/pkgs/development/compilers/llvm/12/default.nix b/pkgs/development/compilers/llvm/12/default.nix
index 388c7d95f69c..e68522faea06 100644
--- a/pkgs/development/compilers/llvm/12/default.nix
+++ b/pkgs/development/compilers/llvm/12/default.nix
@@ -66,14 +66,14 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     # disabled until recommonmark supports sphinx 3
     #Llvm-manpages = lowPrio (tools.libllvm.override {
diff --git a/pkgs/development/compilers/llvm/13/default.nix b/pkgs/development/compilers/llvm/13/default.nix
index 9fd4cd98901d..13be73967143 100644
--- a/pkgs/development/compilers/llvm/13/default.nix
+++ b/pkgs/development/compilers/llvm/13/default.nix
@@ -68,14 +68,14 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     llvm-manpages = lowPrio (tools.libllvm.override {
       enableManpages = true;
diff --git a/pkgs/development/compilers/llvm/5/default.nix b/pkgs/development/compilers/llvm/5/default.nix
index 8205c67da77a..4593580b72fd 100644
--- a/pkgs/development/compilers/llvm/5/default.nix
+++ b/pkgs/development/compilers/llvm/5/default.nix
@@ -39,21 +39,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     llvm-manpages = lowPrio (tools.libllvm.override {
       enableManpages = true;
diff --git a/pkgs/development/compilers/llvm/6/default.nix b/pkgs/development/compilers/llvm/6/default.nix
index 7651b5ab13dc..9b1caf410bc2 100644
--- a/pkgs/development/compilers/llvm/6/default.nix
+++ b/pkgs/development/compilers/llvm/6/default.nix
@@ -39,21 +39,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     llvm-manpages = lowPrio (tools.libllvm.override {
       enableManpages = true;
diff --git a/pkgs/development/compilers/llvm/7/default.nix b/pkgs/development/compilers/llvm/7/default.nix
index 6864353424f1..d014c043a80d 100644
--- a/pkgs/development/compilers/llvm/7/default.nix
+++ b/pkgs/development/compilers/llvm/7/default.nix
@@ -63,21 +63,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     clang-polly-unwrapped = callPackage ./clang {
       inherit llvm_meta;
diff --git a/pkgs/development/compilers/llvm/8/default.nix b/pkgs/development/compilers/llvm/8/default.nix
index 34f204be3315..7252b75a3397 100644
--- a/pkgs/development/compilers/llvm/8/default.nix
+++ b/pkgs/development/compilers/llvm/8/default.nix
@@ -63,21 +63,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     clang-polly-unwrapped = callPackage ./clang {
       inherit llvm_meta;
diff --git a/pkgs/development/compilers/llvm/9/default.nix b/pkgs/development/compilers/llvm/9/default.nix
index 8468fc363818..9126a614b106 100644
--- a/pkgs/development/compilers/llvm/9/default.nix
+++ b/pkgs/development/compilers/llvm/9/default.nix
@@ -63,21 +63,21 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libllvm-polly = callPackage ./llvm {
       inherit llvm_meta;
       enablePolly = true;
     };
 
-    llvm-polly = tools.libllvm-polly.lib // { outputUnspecified = true; };
+    llvm-polly = tools.libllvm-polly.lib // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit clang-tools-extra_src llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     clang-polly-unwrapped = callPackage ./clang {
       inherit llvm_meta;
diff --git a/pkgs/development/compilers/llvm/git/default.nix b/pkgs/development/compilers/llvm/git/default.nix
index 300de57b696e..fb2baf0e29a3 100644
--- a/pkgs/development/compilers/llvm/git/default.nix
+++ b/pkgs/development/compilers/llvm/git/default.nix
@@ -68,14 +68,14 @@ let
     };
 
     # `llvm` historically had the binaries.  When choosing an output explicitly,
-    # we need to reintroduce `outputUnspecified` to get the expected behavior e.g. of lib.get*
-    llvm = tools.libllvm.out // { outputUnspecified = true; };
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm.out // { outputSpecified = false; };
 
     libclang = callPackage ./clang {
       inherit llvm_meta;
     };
 
-    clang-unwrapped = tools.libclang.out // { outputUnspecified = true; };
+    clang-unwrapped = tools.libclang.out // { outputSpecified = false; };
 
     llvm-manpages = lowPrio (tools.libllvm.override {
       enableManpages = true;