diff --git a/libc/src/env.cpp b/libc/src/env.cpp
index 57b8fb34..25812a96 100644
--- a/libc/src/env.cpp
+++ b/libc/src/env.cpp
@@ -94,12 +94,30 @@ static void _update_env()
     environ = g_dynamic_env.data();
 }
 
+// Check if a user has modified environ, in which case we should reset env_is_dynamic and free our buffers.
+static void _check_dynamic_env()
+{
+    if (!env_is_dynamic) return;
+
+    env_is_dynamic = environ == g_dynamic_env.data();
+
+    if (!env_is_dynamic)
+    {
+        for (auto element : g_dynamic_env)
+        {
+            if (element) free(element);
+        }
+    }
+}
+
 extern "C"
 {
     char** environ = nullptr;
 
     int clearenv()
     {
+        _check_dynamic_env();
+
         if (env_is_dynamic)
         {
             for (auto element : g_dynamic_env)
@@ -127,6 +145,8 @@ extern "C"
         auto index = _findenv(key, nullptr);
         if (index < 0) return 0;
 
+        _check_dynamic_env();
+
         if (!env_is_dynamic)
         {
             if (_move_env() < 0) return -1;
@@ -149,6 +169,8 @@ extern "C"
         auto index = _findenv(key, nullptr);
         if (index >= 0 && !overwrite) return 0;
 
+        _check_dynamic_env();
+
         if (!env_is_dynamic)
         {
             if (_move_env() < 0) return -1;
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 7749593c..d090faea 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -21,6 +21,7 @@ luna_test(libluna/TestHashTable.cpp TestHashTable)
 luna_test(libluna/TestCPath.cpp TestCPath)
 luna_test(libc/TestScanf.cpp TestScanf)
 luna_test(libc/TestString.cpp TestString)
+luna_test(libc/TestEnv.cpp TestEnv)
 
 luna_app(run-tests.cpp run-tests)
 endif()
diff --git a/tests/libc/TestEnv.cpp b/tests/libc/TestEnv.cpp
new file mode 100644
index 00000000..b7f076a5
--- /dev/null
+++ b/tests/libc/TestEnv.cpp
@@ -0,0 +1,85 @@
+#include <stdlib.h>
+#include <string.h>
+#include <test.h>
+
+extern char** environ;
+
+TestResult test_setenv_then_getenv()
+{
+    clearenv();
+
+    validate(setenv("sample", "value", 1) == 0);
+
+    char* value = getenv("sample");
+    validate(value);
+    validate(!strcmp(value, "value"));
+
+    test_success;
+}
+
+TestResult test_setenv_dont_overwrite()
+{
+    clearenv();
+
+    validate(setenv("sample", "value", 1) == 0);
+
+    char* value = getenv("sample");
+    validate(value);
+    validate(!strcmp(value, "value"));
+
+    validate(setenv("sample", "other_value", 0) == 0);
+
+    value = getenv("sample");
+    validate(value);
+    validate(!strcmp(value, "value"));
+
+    test_success;
+}
+
+TestResult test_unsetenv()
+{
+    clearenv();
+
+    validate(setenv("sample", "value", 1) == 0);
+
+    char* value = getenv("sample");
+    validate(value);
+    validate(!strcmp(value, "value"));
+
+    validate(unsetenv("sample") == 0);
+
+    value = getenv("sample");
+    validate(!value);
+
+    test_success;
+}
+
+TestResult test_setenv_before_and_after_manual_environ_modification()
+{
+    clearenv();
+
+    validate(setenv("sample", "value", 1) == 0);
+
+    char* list[] = { "hello=world", NULL };
+    environ = list;
+
+    validate(setenv("other", "value", 1) == 0);
+
+    char* value = getenv("hello");
+    validate(value);
+    validate(!strcmp(value, "world"));
+
+    test_success;
+}
+
+Result<void> test_main()
+{
+    test_prelude;
+
+    run_test(test_setenv_then_getenv);
+    run_test(test_setenv_dont_overwrite);
+    run_test(test_unsetenv);
+    run_test(test_setenv_before_and_after_manual_environ_modification);
+
+    return {};
+}