diff --git a/test/test_other.py b/test/test_other.py
index 856d84a72191f..3bff6da7b57c3 100644
--- a/test/test_other.py
+++ b/test/test_other.py
@@ -99,7 +99,7 @@
   with_env_modify,
 )
 
-from tools import building, cache, response_file, shared, utils, webassembly
+from tools import building, cache, ports, response_file, shared, utils, webassembly
 from tools.building import get_building_env
 from tools.cmdline import options
 from tools.link import binary_encode
@@ -2753,6 +2753,17 @@ def test_sdl3_ttf(self):
     self.emcc(test_file('browser/test_sdl3_ttf.c'), args=['-Wno-experimental', '-sUSE_SDL=3', '-sUSE_SDL_TTF=3'])
     self.emcc(test_file('browser/test_sdl3_ttf.c'), args=['-Wno-experimental', '--use-port=sdl3', '--use-port=sdl3_ttf'])
 
+  @requires_network
+  def test_sdl_ttf_parent_cache_lock(self):
+    # Verify that building sdl2_ttf while holding the cache lock (as a parent process does)
+    # succeeds even if libharfbuzz.a is not yet present in the cache.
+    shared.cache.erase_lib('libharfbuzz.a')
+    shared.cache.erase_lib('libSDL2_ttf.a')
+    self.set_setting('USE_SDL', 2)
+    self.set_setting('USE_SDL_TTF', 2)
+    with shared.cache.lock('test_sdl_ttf_parent_cache_lock'):
+      ports.get_port_by_name('sdl2_ttf').get(ports.Ports, settings, shared)
+
   @requires_network
   def test_contrib_ports(self):
     # Verify that contrib ports can be used (using the only contrib port available ATM, but can be replaced
diff --git a/tools/ports/__init__.py b/tools/ports/__init__.py
index 3c9c566a78dd2..5a2e5b912e5d6 100644
--- a/tools/ports/__init__.py
+++ b/tools/ports/__init__.py
@@ -440,6 +440,7 @@ def clear_project_build(name):
   def write_file(filename, contents):
     if os.path.exists(filename) and utils.read_file(filename) == contents:
       return
+    utils.safe_ensure_dirs(os.path.dirname(filename))
     utils.write_file(filename, contents)
 
   @staticmethod
diff --git a/tools/ports/sdl2_ttf.py b/tools/ports/sdl2_ttf.py
index 4e0d75f0e5330..19ef76ac73fb1 100644
--- a/tools/ports/sdl2_ttf.py
+++ b/tools/ports/sdl2_ttf.py
@@ -25,10 +25,15 @@ def get(ports, settings, shared):
   def create(final):
     src_root = ports.get_dir('sdl2_ttf', 'SDL_ttf-' + TAG)
     ports.install_headers(src_root, target='SDL2')
-    flags = ['-DTTF_USE_HARFBUZZ=1', '-sUSE_SDL=2', '-sUSE_FREETYPE', '-sUSE_HARFBUZZ']
+    includes = [
+      ports.get_include_dir('SDL2'),
+      ports.get_include_dir('freetype2'),
+      ports.get_include_dir('harfbuzz'),
+    ]
+    flags = ['-DTTF_USE_HARFBUZZ=1']
     if settings.PTHREADS:
       flags += ['-pthread']
-    ports.build_port(src_root, final, 'sdl2_ttf', flags=flags, srcs=['SDL_ttf.c'])
+    ports.build_port(src_root, final, 'sdl2_ttf', includes=includes, flags=flags, srcs=['SDL_ttf.c'])
 
   return [shared.cache.get_lib(get_lib_name(settings), create, what='port')]
 
diff --git a/tools/ports/sdl3_ttf.py b/tools/ports/sdl3_ttf.py
index 0d4fe4edc2192..67308e548d4b8 100644
--- a/tools/ports/sdl3_ttf.py
+++ b/tools/ports/sdl3_ttf.py
@@ -27,7 +27,13 @@ def get(ports, settings, shared):
   def create(final):
     src_root = ports.get_dir('sdl3_ttf', 'SDL_ttf-' + TAG)
     ports.install_header_dir(os.path.join(src_root, 'include'), target='.')
-    flags = ['-Wno-experimental', '-DTTF_USE_HARFBUZZ=1', '-sUSE_SDL=3', '-sUSE_FREETYPE', '-sUSE_HARFBUZZ']
+    includes = [
+      ports.get_include_dir(),
+      ports.get_include_dir('SDL3'),
+      ports.get_include_dir('freetype2'),
+      ports.get_include_dir('harfbuzz'),
+    ]
+    flags = ['-Wno-experimental', '-DTTF_USE_HARFBUZZ=1']
     if settings.PTHREADS:
       flags += ['-pthread']
 
@@ -40,7 +46,7 @@ def create(final):
       'src/SDL_ttf.c',
     ]
 
-    ports.build_port(src_root, final, 'sdl3_ttf', flags=flags, srcs=srcs)
+    ports.build_port(src_root, final, 'sdl3_ttf', includes=includes, flags=flags, srcs=srcs)
 
   return [shared.cache.get_lib(get_lib_name(settings), create, what='port')]