diff --git a/default.nix b/default.nix
index 7bbd156..3f9416e 100644
--- a/default.nix
+++ b/default.nix
@@ -1,3 +1,4 @@
+{ git-source-repository-overrides ? [ ] }:
 ########################################################################
 # default.nix -- The top-level nix build file for plutus-starter.
 #
@@ -22,7 +23,7 @@ let
   #     haskell-language-server
   #   }
   # }
-  packages = import ./nix;
+  packages = import ./nix { inherit git-source-repository-overrides; };
 
   inherit (packages) pkgs plutus-starter;
   project = plutus-starter.haskell.project;
diff --git a/nix/default.nix b/nix/default.nix
index f85920d..031ef72 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -1,3 +1,4 @@
+{ git-source-repository-overrides ? [ ] }:
 let
   # Pratically, the only needed dependency is the plutus repository.
   sources = import ./sources.nix { inherit pkgs; };
@@ -11,7 +12,7 @@ let
   haskell-nix = pkgs.haskell-nix;
 
   plutus-starter = import ./pkgs {
-    inherit pkgs haskell-nix sources plutus;
+    inherit pkgs haskell-nix sources plutus git-source-repository-overrides;
   };
 
 in
diff --git a/nix/pkgs/default.nix b/nix/pkgs/default.nix
index 9818ca3..1a2bdbc 100644
--- a/nix/pkgs/default.nix
+++ b/nix/pkgs/default.nix
@@ -2,6 +2,7 @@
 , sources
 , plutus
 , haskell-nix
+, git-source-repository-overrides ? [ ]
 }:
 let
   gitignore-nix = pkgs.callPackage plutus."gitignore.nix" { };
@@ -9,7 +10,7 @@ let
   compiler-nix-name = plutus.plutus-apps.haskell.compiler-nix-name;
 
   haskell = pkgs.callPackage ./haskell {
-    inherit gitignore-nix sources haskell-nix;
+    inherit gitignore-nix sources haskell-nix git-source-repository-overrides;
     inherit compiler-nix-name; # Use the same GHC version as plutus
     inherit (pkgs) libsodium-vrf;
   };
diff --git a/nix/pkgs/haskell/default.nix b/nix/pkgs/haskell/default.nix
index aa36c8b..a973b40 100644
--- a/nix/pkgs/haskell/default.nix
+++ b/nix/pkgs/haskell/default.nix
@@ -4,6 +4,7 @@
 , sources
 , compiler-nix-name
 , libsodium-vrf
+, git-source-repository-overrides ? [ ]
 }:
 let
   # The Hackage index-state from cabal.project
@@ -22,7 +23,7 @@ let
 
   # The haskell project created by haskell-nix.cabalProject'
   project = import ./haskell.nix {
-    inherit lib haskell-nix compiler-nix-name gitignore-nix libsodium-vrf;
+    inherit lib haskell-nix compiler-nix-name gitignore-nix libsodium-vrf git-source-repository-overrides;
   };
 
   # All the packages defined by our project, including dependencies
diff --git a/nix/pkgs/haskell/haskell.nix b/nix/pkgs/haskell/haskell.nix
index 8232f38..a996c33 100644
--- a/nix/pkgs/haskell/haskell.nix
+++ b/nix/pkgs/haskell/haskell.nix
@@ -6,10 +6,19 @@
 , compiler-nix-name
 , lib
 , libsodium-vrf
+, git-source-repository-overrides ? [ ]
+  # Override source-repository-package entries in cabal (useful for CI).
+  # Note that this will override any cabal.project.local you have, if set.
+  #
+  # Type: List of attribute sets:
+  #  location
+  #  tag
+  #  sha256
+  #  subdir (optional list of strings)
 }:
 
 let
-  project = haskell-nix.project {
+  project = haskell-nix.project ({
     # 'cleanGit' cleans a source directory based on the files known by git
     src = haskell-nix.haskellLib.cleanGit {
       name = "plutus-starter";
@@ -18,6 +27,8 @@ let
 
     inherit compiler-nix-name;
 
+    # If using materialization, be sure to disable it when git-source-repository-overrides is set or it won't take effect.
+
     sha256map = {
       "https://github.com/input-output-hk/plutus-apps.git"."plutus-starter-devcontainer/v1.0.14" = "0j3hphj4b21vwdj900233d67qsaj91mppwsx1vv0ichnmnw2bmir";
       "https://github.com/Quid2/flat.git"."ee59880f47ab835dbd73bea0847dab7869fc20d8" = "1lrzknw765pz2j97nvv9ip3l1mcpf2zr4n56hwlz0rk7wq7ls4cm";
@@ -37,7 +48,10 @@ let
       "https://github.com/input-output-hk/cardano-wallet"."ae7569293e94241ef6829139ec02bd91abd069df" = "1mv1dhpkdj9ridm1fvq6jc85qs6zvbp172228rq72gyawjwrgvi6";
       "https://github.com/input-output-hk/cardano-addresses"."d2f86caa085402a953920c6714a0de6a50b655ec" = "0p6jbnd7ky2yf7bwb1350k8880py8dgqg39k49q02a6ij4ld01ay";
       "https://github.com/input-output-hk/plutus"."3f089ccf0ca746b399c99afe51e063b0640af547" = "1nx8xmdgwmnsla4qg4k67f5md8vm3p1p9i25ndalrqdg40z90486";
-    };
+    } // (builtins.listToAttrs (map (sro: {
+      name = sro.location;
+      value.${sro.tag} = sro.sha256;
+    }) git-source-repository-overrides));
 
     modules = [
       {
@@ -52,6 +66,17 @@ let
         };
       }
     ];
-  };
+  } // lib.optionalAttrs (git-source-repository-overrides != [ ]) {
+    cabalProjectLocal = builtins.concatStringsSep "\n" (map (sro: ''
+      source-repository-package
+        type: git
+        location: ${sro.location}
+        tag: ${sro.tag}
+    '' + lib.optionalString (sro ? subdir) ''
+        subdir:
+          ${builtins.concatStringsSep "\n    " sro.subdir}
+      -- comment here for proper Nix string indentation
+    '') git-source-repository-overrides);
+  });
 in
   project
diff --git a/release.nix b/release.nix
index dc210b3..43807ad 100644
--- a/release.nix
+++ b/release.nix
@@ -3,7 +3,7 @@
 #
 # Therefore, do not worry too much about the structure.
 let
-  packages = import ./.;
+  packages = import ./. { };
 
   pkgs = packages.pkgs;
   haskellNix = pkgs.haskell-nix;
diff --git a/shell.nix b/shell.nix
index 1eb4811..27186a2 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,6 +1,6 @@
 { pure ? false }:
 let
-  packages = import ./.;
+  packages = import ./. { };
   inherit (packages) pkgs plutus-starter;
   inherit (plutus-starter) haskell;