diff --git a/pkgs/build-support/libredirect/default.nix b/pkgs/build-support/libredirect/default.nix
index 42525ec98a7e..f87c6d23dd79 100644
--- a/pkgs/build-support/libredirect/default.nix
+++ b/pkgs/build-support/libredirect/default.nix
@@ -38,11 +38,11 @@ stdenv.mkDerivation rec {
 
     install -vD "$libName" "$out/lib/$libName"
 
+    # Provide a setup hook that injects our library into every process.
     mkdir -p "$hook/nix-support"
     cat <<SETUP_HOOK > "$hook/nix-support/setup-hook"
     ${if stdenv.isDarwin then ''
     export DYLD_INSERT_LIBRARIES="$out/lib/$libName"
-    export DYLD_FORCE_FLAT_NAMESPACE=1
     '' else ''
     export LD_PRELOAD="$out/lib/$libName"
     ''}
diff --git a/pkgs/build-support/libredirect/libredirect.c b/pkgs/build-support/libredirect/libredirect.c
index c7058ce123c5..7dac4684722f 100644
--- a/pkgs/build-support/libredirect/libredirect.c
+++ b/pkgs/build-support/libredirect/libredirect.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <dlfcn.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -13,6 +14,22 @@
 
 #define MAX_REDIRECTS 128
 
+#ifdef __APPLE__
+  struct dyld_interpose {
+    const void * replacement;
+    const void * replacee;
+  };
+  #define WRAPPER(ret, name) static ret _libredirect_wrapper_##name
+  #define LOOKUP_REAL(name) &name
+  #define WRAPPER_DEF(name) \
+    __attribute__((used)) static struct dyld_interpose _libredirect_interpose_##name \
+      __attribute__((section("__DATA,__interpose"))) = { &_libredirect_wrapper_##name, &name };
+#else
+  #define WRAPPER(ret, name) ret name
+  #define LOOKUP_REAL(name) dlsym(RTLD_NEXT, #name)
+  #define WRAPPER_DEF(name)
+#endif
+
 static int nrRedirects = 0;
 static char * from[MAX_REDIRECTS];
 static char * to[MAX_REDIRECTS];
@@ -80,9 +97,9 @@ static int open_needs_mode(int flags)
    it contains only what we needed for programs in Nixpkgs. Just add
    more functions as needed. */
 
-int open(const char * path, int flags, ...)
+WRAPPER(int, open)(const char * path, int flags, ...)
 {
-    int (*open_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open");
+    int (*open_real) (const char *, int, mode_t) = LOOKUP_REAL(open);
     mode_t mode = 0;
     if (open_needs_mode(flags)) {
         va_list ap;
@@ -93,10 +110,12 @@ int open(const char * path, int flags, ...)
     char buf[PATH_MAX];
     return open_real(rewrite(path, buf), flags, mode);
 }
+WRAPPER_DEF(open)
 
-int open64(const char * path, int flags, ...)
+#ifndef __APPLE__
+WRAPPER(int, open64)(const char * path, int flags, ...)
 {
-    int (*open64_real) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open64");
+    int (*open64_real) (const char *, int, mode_t) = LOOKUP_REAL(open64);
     mode_t mode = 0;
     if (open_needs_mode(flags)) {
         va_list ap;
@@ -107,10 +126,12 @@ int open64(const char * path, int flags, ...)
     char buf[PATH_MAX];
     return open64_real(rewrite(path, buf), flags, mode);
 }
+WRAPPER_DEF(open64)
+#endif
 
-int openat(int dirfd, const char * path, int flags, ...)
+WRAPPER(int, openat)(int dirfd, const char * path, int flags, ...)
 {
-    int (*openat_real) (int, const char *, int, mode_t) = dlsym(RTLD_NEXT, "openat");
+    int (*openat_real) (int, const char *, int, mode_t) = LOOKUP_REAL(openat);
     mode_t mode = 0;
     if (open_needs_mode(flags)) {
         va_list ap;
@@ -121,57 +142,73 @@ int openat(int dirfd, const char * path, int flags, ...)
     char buf[PATH_MAX];
     return openat_real(dirfd, rewrite(path, buf), flags, mode);
 }
+WRAPPER_DEF(openat)
 
-FILE * fopen(const char * path, const char * mode)
+WRAPPER(FILE *, fopen)(const char * path, const char * mode)
 {
-    FILE * (*fopen_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen");
+    FILE * (*fopen_real) (const char *, const char *) = LOOKUP_REAL(fopen);
     char buf[PATH_MAX];
     return fopen_real(rewrite(path, buf), mode);
 }
+WRAPPER_DEF(fopen)
 
-FILE * __nss_files_fopen(const char * path)
+#ifndef __APPLE__
+WRAPPER(FILE *, __nss_files_fopen)(const char * path)
 {
-    FILE * (*__nss_files_fopen_real) (const char *) = dlsym(RTLD_NEXT, "__nss_files_fopen");
+    FILE * (*__nss_files_fopen_real) (const char *) = LOOKUP_REAL(__nss_files_fopen);
     char buf[PATH_MAX];
     return __nss_files_fopen_real(rewrite(path, buf));
 }
+WRAPPER_DEF(__nss_files_fopen)
+#endif
 
-FILE * fopen64(const char * path, const char * mode)
+#ifndef __APPLE__
+WRAPPER(FILE *, fopen64)(const char * path, const char * mode)
 {
-    FILE * (*fopen64_real) (const char *, const char *) = dlsym(RTLD_NEXT, "fopen64");
+    FILE * (*fopen64_real) (const char *, const char *) = LOOKUP_REAL(fopen64);
     char buf[PATH_MAX];
     return fopen64_real(rewrite(path, buf), mode);
 }
+WRAPPER_DEF(fopen64)
+#endif
 
-int __xstat(int ver, const char * path, struct stat * st)
+#ifndef __APPLE__
+WRAPPER(int, __xstat)(int ver, const char * path, struct stat * st)
 {
-    int (*__xstat_real) (int ver, const char *, struct stat *) = dlsym(RTLD_NEXT, "__xstat");
+    int (*__xstat_real) (int ver, const char *, struct stat *) = LOOKUP_REAL(__xstat);
     char buf[PATH_MAX];
     return __xstat_real(ver, rewrite(path, buf), st);
 }
+WRAPPER_DEF(__xstat)
+#endif
 
-int __xstat64(int ver, const char * path, struct stat64 * st)
+#ifndef __APPLE__
+WRAPPER(int, __xstat64)(int ver, const char * path, struct stat64 * st)
 {
-    int (*__xstat64_real) (int ver, const char *, struct stat64 *) = dlsym(RTLD_NEXT, "__xstat64");
+    int (*__xstat64_real) (int ver, const char *, struct stat64 *) = LOOKUP_REAL(__xstat64);
     char buf[PATH_MAX];
     return __xstat64_real(ver, rewrite(path, buf), st);
 }
+WRAPPER_DEF(__xstat64)
+#endif
 
-int stat(const char * path, struct stat * st)
+WRAPPER(int, stat)(const char * path, struct stat * st)
 {
-    int (*__stat_real) (const char *, struct stat *) = dlsym(RTLD_NEXT, "stat");
+    int (*__stat_real) (const char *, struct stat *) = LOOKUP_REAL(stat);
     char buf[PATH_MAX];
     return __stat_real(rewrite(path, buf), st);
 }
+WRAPPER_DEF(stat)
 
-int access(const char * path, int mode)
+WRAPPER(int, access)(const char * path, int mode)
 {
-    int (*access_real) (const char *, int mode) = dlsym(RTLD_NEXT, "access");
+    int (*access_real) (const char *, int mode) = LOOKUP_REAL(access);
     char buf[PATH_MAX];
     return access_real(rewrite(path, buf), mode);
 }
+WRAPPER_DEF(access)
 
-int posix_spawn(pid_t * pid, const char * path,
+WRAPPER(int, posix_spawn)(pid_t * pid, const char * path,
     const posix_spawn_file_actions_t * file_actions,
     const posix_spawnattr_t * attrp,
     char * const argv[], char * const envp[])
@@ -179,12 +216,13 @@ int posix_spawn(pid_t * pid, const char * path,
     int (*posix_spawn_real) (pid_t *, const char *,
         const posix_spawn_file_actions_t *,
         const posix_spawnattr_t *,
-        char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawn");
+        char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawn);
     char buf[PATH_MAX];
     return posix_spawn_real(pid, rewrite(path, buf), file_actions, attrp, argv, envp);
 }
+WRAPPER_DEF(posix_spawn)
 
-int posix_spawnp(pid_t * pid, const char * file,
+WRAPPER(int, posix_spawnp)(pid_t * pid, const char * file,
     const posix_spawn_file_actions_t * file_actions,
     const posix_spawnattr_t * attrp,
     char * const argv[], char * const envp[])
@@ -192,43 +230,48 @@ int posix_spawnp(pid_t * pid, const char * file,
     int (*posix_spawnp_real) (pid_t *, const char *,
         const posix_spawn_file_actions_t *,
         const posix_spawnattr_t *,
-        char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "posix_spawnp");
+        char * const argv[], char * const envp[]) = LOOKUP_REAL(posix_spawnp);
     char buf[PATH_MAX];
     return posix_spawnp_real(pid, rewrite(file, buf), file_actions, attrp, argv, envp);
 }
+WRAPPER_DEF(posix_spawnp)
 
-int execv(const char * path, char * const argv[])
+WRAPPER(int, execv)(const char * path, char * const argv[])
 {
-    int (*execv_real) (const char * path, char * const argv[]) = dlsym(RTLD_NEXT, "execv");
+    int (*execv_real) (const char * path, char * const argv[]) = LOOKUP_REAL(execv);
     char buf[PATH_MAX];
     return execv_real(rewrite(path, buf), argv);
 }
+WRAPPER_DEF(execv)
 
-int execvp(const char * path, char * const argv[])
+WRAPPER(int, execvp)(const char * path, char * const argv[])
 {
-    int (*_execvp) (const char *, char * const argv[]) = dlsym(RTLD_NEXT, "execvp");
+    int (*_execvp) (const char *, char * const argv[]) = LOOKUP_REAL(execvp);
     char buf[PATH_MAX];
     return _execvp(rewrite(path, buf), argv);
 }
+WRAPPER_DEF(execvp)
 
-int execve(const char * path, char * const argv[], char * const envp[])
+WRAPPER(int, execve)(const char * path, char * const argv[], char * const envp[])
 {
-    int (*_execve) (const char *, char * const argv[], char * const envp[]) = dlsym(RTLD_NEXT, "execve");
+    int (*_execve) (const char *, char * const argv[], char * const envp[]) = LOOKUP_REAL(execve);
     char buf[PATH_MAX];
     return _execve(rewrite(path, buf), argv, envp);
 }
+WRAPPER_DEF(execve)
 
-DIR * opendir(const char * path)
+WRAPPER(DIR *, opendir)(const char * path)
 {
     char buf[PATH_MAX];
-    DIR * (*_opendir) (const char*) = dlsym(RTLD_NEXT, "opendir");
+    DIR * (*_opendir) (const char*) = LOOKUP_REAL(opendir);
 
     return _opendir(rewrite(path, buf));
 }
+WRAPPER_DEF(opendir)
 
 #define SYSTEM_CMD_MAX 512
 
-char *replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
+static char * replace_substring(char * source, char * buf, char * replace_string, char * start_ptr, char * suffix_ptr) {
     char head[SYSTEM_CMD_MAX] = {0};
     strncpy(head, source, start_ptr - source);
 
@@ -241,7 +284,7 @@ char *replace_substring(char * source, char * buf, char * replace_string, char *
     return buf;
 }
 
-char *replace_string(char * buf, char * from, char * to) {
+static char * replace_string(char * buf, char * from, char * to) {
     int num_matches = 0;
     char * matches[SYSTEM_CMD_MAX];
     int from_len = strlen(from);
@@ -264,32 +307,48 @@ char *replace_string(char * buf, char * from, char * to) {
     return buf;
 }
 
-void rewriteSystemCall(const char * command, char * buf) {
-    strcpy(buf, command);
+static void rewriteSystemCall(const char * command, char * buf) {
+    char * p = buf;
+
+    #ifdef __APPLE__
+    // The dyld environment variable is not inherited by the subprocess spawned
+    // by system(), so this hack redefines it.
+    Dl_info info;
+    dladdr(&rewriteSystemCall, &info);
+    p = stpcpy(p, "export DYLD_INSERT_LIBRARIES=");
+    p = stpcpy(p, info.dli_fname);
+    p = stpcpy(p, ";");
+    #endif
+
+    stpcpy(p, command);
+
     for (int n = 0; n < nrRedirects; ++n) {
        replace_string(buf, from[n], to[n]);
     }
 }
 
-int system(const char *command)
+WRAPPER(int, system)(const char *command)
 {
-    int (*_system) (const char*) = dlsym(RTLD_NEXT, "system");
+    int (*_system) (const char*) = LOOKUP_REAL(system);
 
     char newCommand[SYSTEM_CMD_MAX];
     rewriteSystemCall(command, newCommand);
     return _system(newCommand);
 }
+WRAPPER_DEF(system)
 
-int mkdir(const char *path, mode_t mode)
+WRAPPER(int, mkdir)(const char *path, mode_t mode)
 {
-    int (*mkdir_real) (const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdir");
+    int (*mkdir_real) (const char *path, mode_t mode) = LOOKUP_REAL(mkdir);
     char buf[PATH_MAX];
     return mkdir_real(rewrite(path, buf), mode);
 }
+WRAPPER_DEF(mkdir)
 
-int mkdirat(int dirfd, const char *path, mode_t mode)
+WRAPPER(int, mkdirat)(int dirfd, const char *path, mode_t mode)
 {
-    int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = dlsym(RTLD_NEXT, "mkdirat");
+    int (*mkdirat_real) (int dirfd, const char *path, mode_t mode) = LOOKUP_REAL(mkdirat);
     char buf[PATH_MAX];
     return mkdirat_real(dirfd, rewrite(path, buf), mode);
 }
+WRAPPER_DEF(mkdirat)