diff --git a/repos/base-hw/src/core/kernel/thread.h b/repos/base-hw/src/core/kernel/thread.h
index 918102a9f..c3a458458 100644
--- a/repos/base-hw/src/core/kernel/thread.h
+++ b/repos/base-hw/src/core/kernel/thread.h
@@ -320,12 +320,14 @@ class Kernel::Thread
 		void user_arg_2(Kernel::Call_arg const arg);
 		void user_arg_3(Kernel::Call_arg const arg);
 		void user_arg_4(Kernel::Call_arg const arg);
+		void user_arg_5(Kernel::Call_arg const arg);
 
 		Kernel::Call_arg user_arg_0() const;
 		Kernel::Call_arg user_arg_1() const;
 		Kernel::Call_arg user_arg_2() const;
 		Kernel::Call_arg user_arg_3() const;
 		Kernel::Call_arg user_arg_4() const;
+		Kernel::Call_arg user_arg_5() const;
 
 		/**
 		 * Syscall to create a thread
diff --git a/repos/base-hw/src/core/spec/arm/kernel/thread.cc b/repos/base-hw/src/core/spec/arm/kernel/thread.cc
index cd3d61391..dd6cb5ac5 100644
--- a/repos/base-hw/src/core/spec/arm/kernel/thread.cc
+++ b/repos/base-hw/src/core/spec/arm/kernel/thread.cc
@@ -104,9 +104,11 @@ void Thread::user_arg_1(Kernel::Call_arg const arg) { regs->r1 = arg; }
 void Thread::user_arg_2(Kernel::Call_arg const arg) { regs->r2 = arg; }
 void Thread::user_arg_3(Kernel::Call_arg const arg) { regs->r3 = arg; }
 void Thread::user_arg_4(Kernel::Call_arg const arg) { regs->r4 = arg; }
+void Thread::user_arg_5(Kernel::Call_arg const arg) { regs->r5 = arg; }
 
 Kernel::Call_arg Thread::user_arg_0() const { return regs->r0; }
 Kernel::Call_arg Thread::user_arg_1() const { return regs->r1; }
 Kernel::Call_arg Thread::user_arg_2() const { return regs->r2; }
 Kernel::Call_arg Thread::user_arg_3() const { return regs->r3; }
 Kernel::Call_arg Thread::user_arg_4() const { return regs->r4; }
+Kernel::Call_arg Thread::user_arg_5() const { return regs->r5; }
diff --git a/repos/base-hw/src/core/spec/arm_v8/kernel/thread.cc b/repos/base-hw/src/core/spec/arm_v8/kernel/thread.cc
index d8f2e0de8..196bf10e4 100644
--- a/repos/base-hw/src/core/spec/arm_v8/kernel/thread.cc
+++ b/repos/base-hw/src/core/spec/arm_v8/kernel/thread.cc
@@ -136,9 +136,11 @@ void Thread::user_arg_1(Kernel::Call_arg const arg) { regs->r[1] = arg; }
 void Thread::user_arg_2(Kernel::Call_arg const arg) { regs->r[2] = arg; }
 void Thread::user_arg_3(Kernel::Call_arg const arg) { regs->r[3] = arg; }
 void Thread::user_arg_4(Kernel::Call_arg const arg) { regs->r[4] = arg; }
+void Thread::user_arg_5(Kernel::Call_arg const arg) { regs->r[5] = arg; }
 
 Kernel::Call_arg Thread::user_arg_0() const { return regs->r[0]; }
 Kernel::Call_arg Thread::user_arg_1() const { return regs->r[1]; }
 Kernel::Call_arg Thread::user_arg_2() const { return regs->r[2]; }
 Kernel::Call_arg Thread::user_arg_3() const { return regs->r[3]; }
 Kernel::Call_arg Thread::user_arg_4() const { return regs->r[4]; }
+Kernel::Call_arg Thread::user_arg_5() const { return regs->r[5]; }
diff --git a/repos/base-hw/src/core/spec/riscv/kernel/thread.cc b/repos/base-hw/src/core/spec/riscv/kernel/thread.cc
index e843499ce..fd81e095d 100644
--- a/repos/base-hw/src/core/spec/riscv/kernel/thread.cc
+++ b/repos/base-hw/src/core/spec/riscv/kernel/thread.cc
@@ -84,8 +84,10 @@ void Thread::user_arg_1(Kernel::Call_arg const arg) { regs->a1  = arg; }
 void Thread::user_arg_2(Kernel::Call_arg const arg) { regs->a2  = arg; }
 void Thread::user_arg_3(Kernel::Call_arg const arg) { regs->a3  = arg; }
 void Thread::user_arg_4(Kernel::Call_arg const arg) { regs->a4  = arg; }
+void Thread::user_arg_5(Kernel::Call_arg const arg) { regs->a5  = arg; }
 Kernel::Call_arg Thread::user_arg_0() const { return regs->a0; }
 Kernel::Call_arg Thread::user_arg_1() const { return regs->a1; }
 Kernel::Call_arg Thread::user_arg_2() const { return regs->a2; }
 Kernel::Call_arg Thread::user_arg_3() const { return regs->a3; }
 Kernel::Call_arg Thread::user_arg_4() const { return regs->a4; }
+Kernel::Call_arg Thread::user_arg_5() const { return regs->a5; }
diff --git a/repos/base-hw/src/core/spec/x86_64/kernel/thread.cc b/repos/base-hw/src/core/spec/x86_64/kernel/thread.cc
index 27084e78c..d6aab3aa1 100644
--- a/repos/base-hw/src/core/spec/x86_64/kernel/thread.cc
+++ b/repos/base-hw/src/core/spec/x86_64/kernel/thread.cc
@@ -70,9 +70,11 @@ void Kernel::Thread::user_arg_1(Kernel::Call_arg const arg) { regs->rsi = arg; }
 void Kernel::Thread::user_arg_2(Kernel::Call_arg const arg) { regs->rdx = arg; }
 void Kernel::Thread::user_arg_3(Kernel::Call_arg const arg) { regs->rcx = arg; }
 void Kernel::Thread::user_arg_4(Kernel::Call_arg const arg) { regs->r8 = arg; }
+void Kernel::Thread::user_arg_5(Kernel::Call_arg const arg) { regs->r9 = arg; }
 
 Kernel::Call_arg Kernel::Thread::user_arg_0() const { return regs->rdi; }
 Kernel::Call_arg Kernel::Thread::user_arg_1() const { return regs->rsi; }
 Kernel::Call_arg Kernel::Thread::user_arg_2() const { return regs->rdx; }
 Kernel::Call_arg Kernel::Thread::user_arg_3() const { return regs->rcx; }
 Kernel::Call_arg Kernel::Thread::user_arg_4() const { return regs->r8; }
+Kernel::Call_arg Kernel::Thread::user_arg_5() const { return regs->r9; }