diff --git a/repos/libports/include/stdcxx/README b/repos/libports/include/stdcxx/README
index 6fca716b82..84fca7fabe 100644
--- a/repos/libports/include/stdcxx/README
+++ b/repos/libports/include/stdcxx/README
@@ -18,3 +18,4 @@ file origins
   - copy 'build/arm_v8a/noux-pkg/gcc_arm_64/aarch64-none-elf/libstdc++-v3/include/aarch64-none-elf/bits/c++config.h'
   - #define _GLIBCXX_HAS_GTHREADS 1 in all of the copied files
   - #undef _GLIBCXX_HAVE_TLS in all of the copied files
+- bits/os_defines.h: manually created, based on config/os/generic/os_defines.h
diff --git a/repos/libports/include/stdcxx/bits/os_defines.h b/repos/libports/include/stdcxx/bits/os_defines.h
new file mode 100644
index 0000000000..604df73c51
--- /dev/null
+++ b/repos/libports/include/stdcxx/bits/os_defines.h
@@ -0,0 +1,35 @@
+/*
+ * \brief  Genode-specific defines
+ * \author Christian Prochaska
+ * \date   2025-03-05
+ */
+
+/*
+ * Copyright (C) 2025 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _INCLUDE__STDCXX__BITS__OS_DEFINES_H_
+#define _INCLUDE__STDCXX__BITS__OS_DEFINES_H_
+
+/* see config/os/generic/os_defines.h */
+#define _GLIBCXX_GTHREAD_USE_WEAK 0
+
+/* prevent gcc headers from defining mbstate */
+#define _GLIBCXX_HAVE_MBSTATE_T 1
+
+/* use compiler-builtin atomic operations */
+#define _GLIBCXX_ATOMIC_BUILTINS 1
+
+/* no isinf isnan */
+#define _GLIBCXX_NO_OBSOLETE_ISINF_ISNAN_DYNAMIC 1
+
+/*
+ * Use 'pthread_mutex_init()' and 'pthread_mutex_destroy()'
+ * instead of 'PTHREAD_MUTEX_INITIALIZER' to avoid memory leaks.
+ */
+#define _GTHREAD_USE_MUTEX_INIT_FUNC 1
+
+#endif /* _INCLUDE__STDCXX__BITS__OS_DEFINES_H_ */
diff --git a/repos/libports/lib/import/import-stdcxx.mk b/repos/libports/lib/import/import-stdcxx.mk
index 0431165dcb..a255e6af15 100644
--- a/repos/libports/lib/import/import-stdcxx.mk
+++ b/repos/libports/lib/import/import-stdcxx.mk
@@ -31,12 +31,3 @@ endif
 
 # stdcxx headers include libc headers
 include $(call select_from_repositories,lib/import/import-libc.mk)
-
-# prevent gcc headers from defining mbstate
-CC_OPT += -D_GLIBCXX_HAVE_MBSTATE_T
-
-# use compiler-builtin atomic operations
-CC_OPT += -D_GLIBCXX_ATOMIC_BUILTINS_4
-
-# No isinf isnan
-CC_OPT += -D_GLIBCXX_NO_OBSOLETE_ISINF_ISNAN_DYNAMIC
diff --git a/repos/libports/ports/stdcxx.hash b/repos/libports/ports/stdcxx.hash
index 904dcd4bc2..9c46073b01 100644
--- a/repos/libports/ports/stdcxx.hash
+++ b/repos/libports/ports/stdcxx.hash
@@ -1 +1 @@
-4eddc2a55a80ed5d3a50fee3f5c25e7ac42afd72
+9bb0da098aecb00b1d9446d45eededda262d6e74
diff --git a/repos/libports/ports/stdcxx.port b/repos/libports/ports/stdcxx.port
index 44cc913447..d15aafce58 100644
--- a/repos/libports/ports/stdcxx.port
+++ b/repos/libports/ports/stdcxx.port
@@ -46,7 +46,6 @@ DIR_CONTENT(include/stdcxx/bits) := \
     src/lib/stdcxx/config/os/generic/ctype_base.h \
     src/lib/stdcxx/config/os/generic/ctype_inline.h \
     src/lib/stdcxx/config/os/generic/error_constants.h \
-    src/lib/stdcxx/config/os/generic/os_defines.h \
     src/lib/stdcxx/config/locale/generic/messages_members.h \
     src/lib/stdcxx/config/locale/generic/time_members.h \
     src/lib/stdcxx/gthr.h