diff --git a/src/libfetchers/git-utils.cc b/src/libfetchers/git-utils.cc
index a4a00374c19..acc623c5d3e 100644
--- a/src/libfetchers/git-utils.cc
+++ b/src/libfetchers/git-utils.cc
@@ -1,3 +1,4 @@
+#include "environment-variables.hh"
 #include "git-utils.hh"
 #include "fs-input-accessor.hh"
 #include "input-accessor.hh"
@@ -377,18 +378,23 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
         auto dir = this->path;
         Strings gitArgs;
         if (shallow) {
-            gitArgs = { "-C", dir.string(), "fetch", "--quiet", "--force", "--depth", "1", "--", url, refspec };
+            gitArgs = { "fetch", "--quiet", "--force", "--depth", "1", "--", url, refspec };
         }
         else {
-            gitArgs = { "-C", dir.string(), "fetch", "--quiet", "--force", "--", url, refspec };
+            gitArgs = { "fetch", "--quiet", "--force", "--", url, refspec };
         }
 
+
+        std::map<std::string, std::string> gitEnv = getEnv();
+        gitEnv.emplace("GIT_DIR", dir.string());
+
         runProgram(RunOptions {
             .program = "git",
             .searchPath = true,
             // FIXME: git stderr messes up our progress indicator, so
             // we're using --quiet for now. Should process its stderr.
             .args = gitArgs,
+            .environment = gitEnv,
             .input = {},
             .isInteractive = true
         });
diff --git a/src/libfetchers/unix/git.cc b/src/libfetchers/unix/git.cc
index 18915c0a7a0..b980e64317f 100644
--- a/src/libfetchers/unix/git.cc
+++ b/src/libfetchers/unix/git.cc
@@ -167,11 +167,16 @@ struct GitInputScheme : InputScheme
 {
     std::optional<Input> inputFromURL(const ParsedURL & url, bool requireTree) const override
     {
+        if (url.scheme != "git" && url.scheme.compare(0, 4, "git+") != 0)
+            return {};
+
         if (url.scheme != "git" &&
             url.scheme != "git+http" &&
             url.scheme != "git+https" &&
             url.scheme != "git+ssh" &&
-            url.scheme != "git+file") return {};
+            url.scheme != "git+file")
+            warn("URL scheme '%s' is non-standard and requires 'git-remote-%s'.", url.scheme, url.scheme.substr(4, url.scheme.length() - 4));
+
 
         auto url2(url);
         if (hasPrefix(url2.scheme, "git+")) url2.scheme = std::string(url2.scheme, 4);