diff --git a/libexec/rtld-elf/aarch64/reloc.c b/libexec/rtld-elf/aarch64/reloc.c
--- a/libexec/rtld-elf/aarch64/reloc.c
+++ b/libexec/rtld-elf/aarch64/reloc.c
@@ -521,7 +521,8 @@
 	* use.
 	*/
 	tls_static_space = tls_last_offset + tls_last_size +
-	    RTLD_STATIC_TLS_EXTRA;
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	_tcb_set(allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN));
 }
diff --git a/libexec/rtld-elf/amd64/reloc.c b/libexec/rtld-elf/amd64/reloc.c
--- a/libexec/rtld-elf/amd64/reloc.c
+++ b/libexec/rtld-elf/amd64/reloc.c
@@ -527,7 +527,9 @@
 	 * offset allocated so far and adding a bit for dynamic
 	 * modules to use.
 	 */
-	tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
+	tls_static_space = tls_last_offset +
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	addr = allocate_tls(objs, 0, TLS_TCB_SIZE, TLS_TCB_ALIGN);
 
diff --git a/libexec/rtld-elf/arm/reloc.c b/libexec/rtld-elf/arm/reloc.c
--- a/libexec/rtld-elf/arm/reloc.c
+++ b/libexec/rtld-elf/arm/reloc.c
@@ -454,7 +454,9 @@
 	* use.
 	*/
 
-	tls_static_space = tls_last_offset + tls_last_size + RTLD_STATIC_TLS_EXTRA;
+	tls_static_space = tls_last_offset + tls_last_size +
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	_tcb_set(allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN));
 }
diff --git a/libexec/rtld-elf/i386/reloc.c b/libexec/rtld-elf/i386/reloc.c
--- a/libexec/rtld-elf/i386/reloc.c
+++ b/libexec/rtld-elf/i386/reloc.c
@@ -510,7 +510,9 @@
      * offset allocated so far and adding a bit for dynamic modules to
      * use.
      */
-    tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
+    tls_static_space = tls_last_offset +
+	(ld_optional_static_tls ? ld_optional_static_tls :
+	RTLD_STATIC_TLS_EXTRA);
     tls = allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN);
     _tcb_set(tls);
 }
diff --git a/libexec/rtld-elf/powerpc/reloc.c b/libexec/rtld-elf/powerpc/reloc.c
--- a/libexec/rtld-elf/powerpc/reloc.c
+++ b/libexec/rtld-elf/powerpc/reloc.c
@@ -817,7 +817,9 @@
 	* use.
 	*/
 
-	tls_static_space = tls_last_offset + tls_last_size + RTLD_STATIC_TLS_EXTRA;
+	tls_static_space = tls_last_offset + tls_last_size +
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	_tcb_set(allocate_tls(list, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN));
 }
diff --git a/libexec/rtld-elf/powerpc64/reloc.c b/libexec/rtld-elf/powerpc64/reloc.c
--- a/libexec/rtld-elf/powerpc64/reloc.c
+++ b/libexec/rtld-elf/powerpc64/reloc.c
@@ -714,7 +714,9 @@
 	* use.
 	*/
 
-	tls_static_space = tls_last_offset + tls_last_size + RTLD_STATIC_TLS_EXTRA;
+	tls_static_space = tls_last_offset + tls_last_size +
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	_tcb_set(allocate_tls(list, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN));
 }
diff --git a/libexec/rtld-elf/riscv/reloc.c b/libexec/rtld-elf/riscv/reloc.c
--- a/libexec/rtld-elf/riscv/reloc.c
+++ b/libexec/rtld-elf/riscv/reloc.c
@@ -392,7 +392,8 @@
 	 * use.
 	 */
 	tls_static_space = tls_last_offset + tls_last_size +
-	    RTLD_STATIC_TLS_EXTRA;
+	    (ld_optional_static_tls ? ld_optional_static_tls :
+	    RTLD_STATIC_TLS_EXTRA);
 
 	_tcb_set(allocate_tls(objs, NULL, TLS_TCB_SIZE, TLS_TCB_ALIGN));
 }
diff --git a/libexec/rtld-elf/rtld.h b/libexec/rtld-elf/rtld.h
--- a/libexec/rtld-elf/rtld.h
+++ b/libexec/rtld-elf/rtld.h
@@ -50,6 +50,7 @@
 extern size_t tls_static_space;
 extern Elf_Addr tls_dtv_generation;
 extern int tls_max_index;
+extern size_t ld_optional_static_tls;
 
 extern int npagesizes;
 extern size_t *pagesizes;
diff --git a/libexec/rtld-elf/rtld.1 b/libexec/rtld-elf/rtld.1
--- a/libexec/rtld-elf/rtld.1
+++ b/libexec/rtld-elf/rtld.1
@@ -26,7 +26,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd November 10, 2022
+.Dd September 29, 2023
 .Dt RTLD 1
 .Os
 .Sh NAME
@@ -320,6 +320,11 @@
 .Nm
 to dump content of the aux vector to standard output, before passing
 control to any user code.
+.It Ev LD_OPTIONAL_STATIC_TLS
+If the variable is specified and has a numeric value,
+.Nm
+will set the size of the static TLS space to the specified number of
+bytes. The minimum value that can be specified is \'128\'.
 .El
 .Sh DIRECT EXECUTION MODE
 .Nm
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -225,6 +225,7 @@
 static Obj_Entry obj_rtld;	/* The dynamic linker shared object */
 static unsigned int obj_count;	/* Number of objects in obj_list */
 static unsigned int obj_loads;	/* Number of loads of objects (gen count) */
+size_t ld_optional_static_tls;	/* Optional static TLS space (bytes) */
 
 static Objlist list_global =	/* Objects dlopened with RTLD_GLOBAL */
   STAILQ_HEAD_INITIALIZER(list_global);
@@ -365,6 +366,7 @@
 	LD_TRACE_LOADED_OBJECTS_FMT2,
 	LD_TRACE_LOADED_OBJECTS_ALL,
 	LD_SHOW_AUXV,
+	LD_OPTIONAL_STATIC_TLS,
 };
 
 struct ld_env_var_desc {
@@ -398,6 +400,7 @@
 	LD_ENV_DESC(TRACE_LOADED_OBJECTS_FMT2, false),
 	LD_ENV_DESC(TRACE_LOADED_OBJECTS_ALL, false),
 	LD_ENV_DESC(SHOW_AUXV, false),
+	LD_ENV_DESC(OPTIONAL_STATIC_TLS, false),
 };
 
 static const char *
@@ -515,7 +518,7 @@
     struct stat st;
     Elf_Addr *argcp;
     char **argv, **env, **envp, *kexecpath;
-    const char *argv0, *binpath, *library_path_rpath;
+    const char *argv0, *binpath, *library_path_rpath, *optional_static_tls;
     struct ld_env_var_desc *lvd;
     caddr_t imgentry;
     char buf[MAXPATHLEN];
@@ -738,9 +741,20 @@
 	    else
 		    ld_library_path_rpath = false;
     }
+    optional_static_tls = ld_get_env_var(LD_OPTIONAL_STATIC_TLS);
+    if (optional_static_tls != NULL && optional_static_tls[0] != '\0') {
+	ld_optional_static_tls = parse_integer(optional_static_tls);
+	if (ld_optional_static_tls < RTLD_STATIC_TLS_EXTRA ||
+	    ld_optional_static_tls > SIZE_T_MAX) {
+	    _rtld_error("invalid optional static TLS setting: %s",
+	        optional_static_tls);
+	    rtld_die();
+	}
+    }
     dangerous_ld_env = libmap_disable || libmap_override != NULL ||
 	ld_library_path != NULL || ld_preload != NULL ||
-	ld_elf_hints_path != NULL || ld_loadfltr || !ld_dynamic_weak;
+	ld_elf_hints_path != NULL || ld_loadfltr || !ld_dynamic_weak ||
+	ld_optional_static_tls;
     ld_tracing = ld_get_env_var(LD_TRACE_LOADED_OBJECTS);
     ld_utrace = ld_get_env_var(LD_UTRACE);