diff --git a/src/highlight/file_tester.rs b/src/highlight/file_tester.rs
index 8149f0fe5..803f8dcfd 100644
--- a/src/highlight/file_tester.rs
+++ b/src/highlight/file_tester.rs
@@ -8,7 +8,6 @@
     VARIABLE_EXPAND, VARIABLE_EXPAND_SINGLE,
 };
 use crate::expand::{expand_tilde, ExpandFlags, HOME_DIRECTORY};
-use crate::libc::_PC_CASE_SENSITIVE;
 use crate::operation_context::OperationContext;
 use crate::path::path_apply_working_directory;
 use crate::redirection::RedirectionMode;
@@ -23,7 +22,6 @@
     dir_iter::DirIter, fish_wcstoi, normalize_path, waccess, wbasename, wdirname, wstat,
 };
 use libc::PATH_MAX;
-use std::collections::hash_map::Entry;
 use std::collections::{HashMap, HashSet};
 use std::os::fd::RawFd;
 
@@ -391,27 +389,30 @@ pub fn is_potential_cd_path(
 ///     false: the filesystem is not case insensitive
 ///     true: the file system is case insensitive
 pub type CaseSensitivityCache = HashMap<WString, bool>;
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
 fn fs_is_case_insensitive(
     path: &wstr,
     fd: RawFd,
     case_sensitivity_cache: &mut CaseSensitivityCache,
 ) -> bool {
-    let mut result = false;
-    if *_PC_CASE_SENSITIVE != 0 {
-        // Try the cache first.
-        match case_sensitivity_cache.entry(path.to_owned()) {
-            Entry::Occupied(e) => {
-                /* Use the cached value */
-                result = *e.get();
-            }
-            Entry::Vacant(e) => {
-                // Ask the system. A -1 value means error (so assume case sensitive), a 1 value means case
-                // sensitive, and a 0 value means case insensitive.
-                let ret = unsafe { libc::fpathconf(fd, *_PC_CASE_SENSITIVE) };
-                result = ret == 0;
-                e.insert(result);
-            }
-        }
-    }
-    result
+    if let Some(cached) = case_sensitivity_cache.get(path) {
+        return *cached;
+    };
+    // Ask the system. A -1 value means error (so assume case sensitive), a 1 value means case
+    // sensitive, and a 0 value means case insensitive.
+    let ret = unsafe { libc::fpathconf(fd, libc::_PC_CASE_SENSITIVE) };
+    let icase = ret == 0;
+    case_sensitivity_cache.insert(path.to_owned(), icase);
+    icase
+}
+
+#[cfg(not(any(target_os = "macos", target_os = "ios")))]
+pub fn fs_is_case_insensitive(
+    _path: &wstr,
+    _fd: RawFd,
+    _case_sensitivity_cache: &mut CaseSensitivityCache,
+) -> bool {
+    // Other platforms don’t have _PC_CASE_SENSITIVE.
+    false
 }
diff --git a/src/libc.c b/src/libc.c
index 072609ef5..dc327c9fd 100644
--- a/src/libc.c
+++ b/src/libc.c
@@ -7,7 +7,7 @@
 #include <sys/mount.h>  // MNT_LOCAL
 #include <sys/resource.h>
 #include <sys/statvfs.h>  // ST_LOCAL
-#include <unistd.h>       // _PC_CASE_SENSITIVE
+#include <unistd.h>
 
 uint64_t C_ST_LOCAL() {
 #if defined(ST_LOCAL)
@@ -27,14 +27,6 @@ uint64_t C_MNT_LOCAL() {
 
 const char* C_PATH_BSHELL() { return _PATH_BSHELL; }
 
-int C_PC_CASE_SENSITIVE() {
-#ifdef _PC_CASE_SENSITIVE
-    return _PC_CASE_SENSITIVE;
-#else
-    return 0;
-#endif
-}
-
 FILE* stdout_stream() { return stdout; }
 
 int C_RLIMIT_CORE() { return RLIMIT_CORE; }
diff --git a/src/libc.rs b/src/libc.rs
index ba1791fea..bb26edb0d 100644
--- a/src/libc.rs
+++ b/src/libc.rs
@@ -1,18 +1,12 @@
 use std::sync::atomic::AtomicPtr;
 
-use libc::{c_char, c_int};
-use once_cell::sync::Lazy;
+use libc::c_char;
 
 pub static _PATH_BSHELL: AtomicPtr<c_char> = AtomicPtr::new(std::ptr::null_mut());
 extern "C" {
     pub fn C_PATH_BSHELL() -> *const c_char;
 }
 
-pub static _PC_CASE_SENSITIVE: Lazy<c_int> = Lazy::new(|| unsafe { C_PC_CASE_SENSITIVE() });
-extern "C" {
-    fn C_PC_CASE_SENSITIVE() -> c_int;
-}
-
 extern "C" {
     pub fn stdout_stream() -> *mut libc::FILE;
     pub fn setlinebuf(stream: *mut libc::FILE);