diff --git a/src/nix/command.cc b/src/nix/command.cc
index 111b5a10f..4520309cd 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -142,4 +142,48 @@ MixDefaultProfile::MixDefaultProfile()
     profile = getDefaultProfile();
 }
 
+MixEnvironment::MixEnvironment() : ignoreEnvironment(false) {
+    mkFlag()
+        .longName("ignore-environment")
+        .shortName('i')
+        .description("clear the entire environment (except those specified with --keep)")
+        .set(&ignoreEnvironment, true);
+
+    mkFlag()
+        .longName("keep")
+        .shortName('k')
+        .description("keep specified environment variable")
+        .arity(1)
+        .labels({"name"})
+        .handler([&](std::vector<std::string> ss) { keep.insert(ss.front()); });
+
+    mkFlag()
+        .longName("unset")
+        .shortName('u')
+        .description("unset specified environment variable")
+        .arity(1)
+        .labels({"name"})
+        .handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
+}
+
+void MixEnvironment::setEnviron() {
+    if (ignoreEnvironment) {
+        if (!unset.empty())
+            throw UsageError("--unset does not make sense with --ignore-environment");
+
+        for (const auto & var : keep) {
+            auto val = getenv(var.c_str());
+            if (val) stringsEnv.emplace_back(fmt("%s=%s", var.c_str(), val));
+        }
+        vectorEnv = stringsToCharPtrs(stringsEnv);
+        environ = vectorEnv.data();
+    } else {
+        if (!keep.empty())
+            throw UsageError("--keep does not make sense without --ignore-environment");
+
+        for (const auto & var : unset)
+            unsetenv(var.c_str());
+    }
+}
+
 }
diff --git a/src/nix/command.hh b/src/nix/command.hh
index 42c14927f..16f8997dd 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -200,4 +200,17 @@ struct MixDefaultProfile : MixProfile
     MixDefaultProfile();
 };
 
-}
+struct MixEnvironment : virtual Args {
+
+    StringSet keep, unset;
+    Strings stringsEnv;
+    std::vector<char*> vectorEnv;
+    bool ignoreEnvironment;
+
+    MixEnvironment();
+
+    /* Modify global environ based on ignoreEnvironment, keep, and unset. It's expected that exec will be called before this class goes out of scope, otherwise environ will become invalid. */
+    void setEnviron();
+};
+
+}
\ No newline at end of file
diff --git a/src/nix/run.cc b/src/nix/run.cc
index ed15527b8..0fbd0b8a8 100644
--- a/src/nix/run.cc
+++ b/src/nix/run.cc
@@ -57,11 +57,9 @@ struct RunCommon : virtual Command
     }
 };
 
-struct CmdRun : InstallablesCommand, RunCommon
+struct CmdRun : InstallablesCommand, RunCommon, MixEnvironment
 {
     std::vector<std::string> command = { "bash" };
-    StringSet keep, unset;
-    bool ignoreEnvironment = false;
 
     CmdRun()
     {
@@ -75,28 +73,6 @@ struct CmdRun : InstallablesCommand, RunCommon
                 if (ss.empty()) throw UsageError("--command requires at least one argument");
                 command = ss;
             });
-
-        mkFlag()
-            .longName("ignore-environment")
-            .shortName('i')
-            .description("clear the entire environment (except those specified with --keep)")
-            .set(&ignoreEnvironment, true);
-
-        mkFlag()
-            .longName("keep")
-            .shortName('k')
-            .description("keep specified environment variable")
-            .arity(1)
-            .labels({"name"})
-            .handler([&](std::vector<std::string> ss) { keep.insert(ss.front()); });
-
-        mkFlag()
-            .longName("unset")
-            .shortName('u')
-            .description("unset specified environment variable")
-            .arity(1)
-            .labels({"name"})
-            .handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
     }
 
     std::string description() override
@@ -132,35 +108,13 @@ struct CmdRun : InstallablesCommand, RunCommon
 
         auto accessor = store->getFSAccessor();
 
-        if (ignoreEnvironment) {
-
-            if (!unset.empty())
-                throw UsageError("--unset does not make sense with --ignore-environment");
-
-            std::map<std::string, std::string> kept;
-            for (auto & var : keep) {
-                auto s = getenv(var.c_str());
-                if (s) kept[var] = s;
-            }
-
-            clearEnv();
-
-            for (auto & var : kept)
-                setenv(var.first.c_str(), var.second.c_str(), 1);
-
-        } else {
-
-            if (!keep.empty())
-                throw UsageError("--keep does not make sense without --ignore-environment");
-
-            for (auto & var : unset)
-                unsetenv(var.c_str());
-        }
 
         std::unordered_set<Path> done;
         std::queue<Path> todo;
         for (auto & path : outPaths) todo.push(path);
 
+        setEnviron();
+
         auto unixPath = tokenizeString<Strings>(getEnv("PATH"), ":");
 
         while (!todo.empty()) {
diff --git a/src/nix/shell.cc b/src/nix/shell.cc
index 6fa471dfc..2c5142518 100644
--- a/src/nix/shell.cc
+++ b/src/nix/shell.cc
@@ -231,7 +231,7 @@ struct Common : InstallableCommand, MixProfile
     }
 };
 
-struct CmdDevShell : Common
+struct CmdDevShell : Common, MixEnvironment
 {
     std::string description() override
     {
@@ -277,6 +277,8 @@ struct CmdDevShell : Common
 
         auto shell = getEnv("SHELL", "bash");
 
+        setEnviron();
+
         auto args = Strings{baseNameOf(shell), "--rcfile", rcFilePath};
 
         restoreAffinity();