diff --git a/rakelib/boot.rake b/rakelib/boot.rake
index 46ba65a..9f3d271 100644
--- a/rakelib/boot.rake
+++ b/rakelib/boot.rake
@@ -16,7 +16,7 @@ def gcc_verbose(gcc_binary)
   output
 end
 
-def find_build_target(gcc_version)
+def find_build_target
   gcc_verbose('gcc')
     .lines
     .find { |line| line.start_with? 'Target: ' }
@@ -61,6 +61,7 @@ namespace :boot do
   # Dependencies.
   GCC_VERSION = "15.1.0"
   HOST_GCC = TMP + 'host/gcc'
+  GCC_PATCH = 'https://raw.githubusercontent.com/Homebrew/formula-patches/575ffcaed6d3112916fed77d271dd3799a7255c4/gcc/gcc-15.1.0.diff'
 
   directory HOST_GCC
   directory(TMP + 'tools')
@@ -68,30 +69,32 @@ namespace :boot do
   desc 'Download and configure the bootstrap compiler'
   task configure: [TMP + 'tools', HOST_GCC, HOST_INSTALL] do
     url = URI.parse "https://gcc.gnu.org/pub/gcc/releases/gcc-#{GCC_VERSION}/gcc-#{GCC_VERSION}.tar.xz"
-    build_target = find_build_target GCC_VERSION
+    build_target = find_build_target
     source_directory = TMP + "tools/gcc-#{GCC_VERSION}"
     frontend_link = source_directory + 'gcc'
 
     download_and_pipe url, source_directory.dirname, ['tar', '-Jxv']
+    download_and_pipe URI.parse(GCC_PATCH), source_directory, ['patch', '-p1']
 
     sh 'contrib/download_prerequisites', chdir: source_directory.to_path
     File.symlink Pathname.new('.').relative_path_from(frontend_link), (frontend_link + 'elna')
 
     configure_options = [
       "--prefix=#{HOST_INSTALL.realpath}",
-      '--with-sysroot=/',
-      '--enable-languages=c,c++,m2,elna',
+      '--enable-languages=c,c++,elna',
       '--disable-bootstrap',
       '--disable-multilib',
+      '--with-system-zlib',
       "--target=#{build_target}",
       "--build=#{build_target}",
       "--host=#{build_target}"
     ]
-    flags = '-O0 -g -fPIC'
-    env = {
-      'CFLAGS' => flags,
-      'CXXFLAGS' => flags,
-    }
+    if File.symlink? '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk'
+      configure_options << '--with-sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk'
+    end
+    env = ENV.slice 'CC', 'CXX'
+    env['CFLAGS'] = env['CXXFLAGS'] = '-O0 -g -fPIC -I/opt/homebrew/opt/flex/include'
+
     configure = source_directory.relative_path_from(HOST_GCC) + 'configure'
     sh env, configure.to_path, *configure_options, chdir: HOST_GCC
   end