diff --git a/builder/default.nix b/builder/default.nix
index 75f0043..bfe3298 100644
--- a/builder/default.nix
+++ b/builder/default.nix
@@ -8,11 +8,14 @@
 }:
 let
 
+  parseGoMod = import ./parser.nix;
+
   removeExpr = refs: ''remove-references-to ${lib.concatMapStrings (ref: " -t ${ref}") refs}'';
 
   buildGoApplication =
     { modules
     , src
+    , pwd ? null
     , CGO_ENABLED ? "0"
     , nativeBuildInputs ? [ ]
     , allowGoReference ? false
@@ -23,6 +26,22 @@ let
     let
       modulesStruct = builtins.fromTOML (builtins.readFile modules);
 
+      goMod = parseGoMod (builtins.readFile "${builtins.toString pwd}/go.mod");
+      localReplaceCommands =
+        let
+          localReplaceAttrs = lib.filterAttrs (n: v: lib.hasAttr "path" v) goMod.replace;
+          commands = (
+            lib.mapAttrsToList
+              (name: value: (
+                ''
+                  mkdir -p $(dirname vendor/${name})
+                  ln -s ${pwd + "/${value.path}"} vendor/${name}
+                ''
+              ))
+              localReplaceAttrs);
+        in
+        if pwd != null then commands else [ ];
+
       vendorEnv = runCommand "vendor-env"
         {
           nativeBuildInputs = [ go ];
@@ -50,6 +69,9 @@ let
             export GOPATH="$TMPDIR/go"
 
             go run ${./symlink.go}
+            ${lib.concatStringsSep "\n" localReplaceCommands}
+
+            find vendor
 
             mv vendor $out
           ''
diff --git a/builder/parser.nix b/builder/parser.nix
new file mode 100644
index 0000000..3c6131d
--- /dev/null
+++ b/builder/parser.nix
@@ -0,0 +1,134 @@
+# Parse go.mod in Nix
+# Returns a Nix structure with the contents of the go.mod passed in
+# in normalised form.
+
+let
+  inherit (builtins) elemAt mapAttrs split foldl' match filter typeOf;
+
+  # Strip lines with comments & other junk
+  stripStr = s: elemAt (split "^ *" (elemAt (split " *$" s) 0)) 2;
+  stripLines = initialLines: foldl' (acc: f: f acc) initialLines [
+    # Strip comments
+    (lines: map
+      (l:
+        let
+          m = match "(.*)( |)//.*" l;
+          hasComment = m != null;
+        in
+        stripStr (if hasComment then elemAt m 0 else l))
+      lines)
+
+    # Strip leading tabs characters
+    (lines: map (l: elemAt (match "(\t|)(.*)" l) 1) lines)
+
+    # Filter empty lines
+    (filter (l: l != ""))
+  ];
+
+  # Parse lines into a structure
+  parseLines = lines: (foldl'
+    (acc: l:
+      let
+        m = match "([^ )]*) *(.*)" l;
+        directive = elemAt m 0;
+        rest = elemAt m 1;
+
+        # Maintain parser state (inside parens or not)
+        inDirective =
+          if rest == "(" then directive
+          else if rest == ")" then null
+          else acc.inDirective
+        ;
+
+      in
+      {
+        data = acc.data // (
+          if directive == "" && rest == ")" then { }
+          else if inDirective != null && rest == "(" then {
+            ${inDirective} = { };
+          } else if inDirective != null then {
+            ${inDirective} = acc.data.${inDirective} // { ${directive} = rest; };
+          } else {
+            ${directive} = rest;
+          }
+        );
+        inherit inDirective;
+      })
+    {
+      inDirective = null;
+      data = { };
+    }
+    lines
+  ).data;
+
+  normaliseDirectives = data: (
+    let
+      normaliseString = s:
+        let
+          m = builtins.match "([^ ]+) (.+)" s;
+        in
+        {
+          ${elemAt m 0} = elemAt m 1;
+        };
+      require = data.require or { };
+      replace = data.replace or { };
+      exclude = data.exclude or { };
+    in
+    data // {
+      require =
+        if typeOf require == "string" then normaliseString require
+        else require;
+      replace =
+        if typeOf replace == "string" then normaliseString replace
+        else replace;
+    }
+  );
+
+  parseVersion = ver:
+    let
+      m = elemAt (match "([^-]+)-?([^-]*)-?([^-]*)" ver);
+      v = elemAt (match "([^+]+)\\+?(.*)" (m 0));
+    in
+    {
+      version = v 0;
+      versionSuffix = v 1;
+      date = m 1;
+      rev = m 2;
+    };
+
+  parseReplace = data: (
+    data // {
+      replace =
+        mapAttrs
+          (n: v:
+            let
+              m = match "=> (.+?) (.+)" v;
+              m2 = match "=> (.*+)" v;
+            in
+            if m != null then {
+              goPackagePath = elemAt m 0;
+              version = parseVersion (elemAt m 1);
+            } else {
+              path = elemAt m2 0;
+            })
+          data.replace;
+    }
+  );
+
+  parseRequire = data: (
+    data // {
+      require = mapAttrs (n: v: parseVersion v) data.require;
+    }
+  );
+
+  splitString = sep: s: filter (t: t != [ ]) (split sep s);
+
+in
+contents:
+foldl' (acc: f: f acc) (splitString "\n" contents) [
+  stripLines
+  parseLines
+  normaliseDirectives
+  parseReplace
+  parseRequire
+]