diff --git a/pkgs/build-support/fetchgit/default.nix b/pkgs/build-support/fetchgit/default.nix
index 45c7599b1c74..a620f6c09a00 100644
--- a/pkgs/build-support/fetchgit/default.nix
+++ b/pkgs/build-support/fetchgit/default.nix
@@ -60,6 +60,7 @@ lib.makeOverridable (
       # Impure env vars (https://nixos.org/nix/manual/#sec-advanced-attributes)
       # needed for netrcPhase
       netrcImpureEnvVars ? [ ],
+      passthru ? { },
       meta ? { },
       allowedRequisites ? null,
       # fetch all tags after tree (useful for git describe)
@@ -195,7 +196,8 @@ lib.makeOverridable (
         passthru = {
           gitRepoUrl = url;
           inherit tag;
-        };
+        }
+        // passthru;
       }
   )
 )
diff --git a/pkgs/build-support/fetchgithub/default.nix b/pkgs/build-support/fetchgithub/default.nix
index dfe210f32c41..c25c86e6f772 100644
--- a/pkgs/build-support/fetchgithub/default.nix
+++ b/pkgs/build-support/fetchgithub/default.nix
@@ -22,6 +22,7 @@ lib.makeOverridable (
     sparseCheckout ? lib.optional (rootDir != "") rootDir,
     githubBase ? "github.com",
     varPrefix ? null,
+    passthru ? { },
     meta ? { },
     ... # For hash agility
   }@args:
@@ -112,7 +113,8 @@ lib.makeOverridable (
     revWithTag = if tag != null then "refs/tags/${tag}" else rev;
 
     fetcherArgs =
-      (
+      passthruAttrs
+      // (
         if useFetchGit then
           {
             inherit
@@ -124,6 +126,7 @@ lib.makeOverridable (
               fetchLFS
               ;
             url = gitRepoUrl;
+            inherit passthru;
           }
           // lib.optionalAttrs (leaveDotGit != null) { inherit leaveDotGit; }
         else
@@ -148,11 +151,11 @@ lib.makeOverridable (
 
             passthru = {
               inherit gitRepoUrl;
-            };
+            }
+            // passthru;
           }
       )
       // privateAttrs
-      // passthruAttrs
       // {
         inherit name;
       };