diff --git a/lib/libthr/arch/aarch64/include/pthread_md.h b/lib/libthr/arch/aarch64/include/pthread_md.h
--- a/lib/libthr/arch/aarch64/include/pthread_md.h
+++ b/lib/libthr/arch/aarch64/include/pthread_md.h
@@ -51,4 +51,6 @@
 	return (_tcb_get()->tcb_thread);
 }
 
+#define	_cfi_undefine_ra()	__asm __volatile(".cfi_undefined x30")
+
 #endif /* _PTHREAD_MD_H_ */
diff --git a/lib/libthr/arch/amd64/include/pthread_md.h b/lib/libthr/arch/amd64/include/pthread_md.h
--- a/lib/libthr/arch/amd64/include/pthread_md.h
+++ b/lib/libthr/arch/amd64/include/pthread_md.h
@@ -56,4 +56,6 @@
 
 #define	HAS__UMTX_OP_ERR	1
 
+#define	_cfi_undefine_ra()	__asm __volatile(".cfi_undefined %rip")
+
 #endif
diff --git a/lib/libthr/arch/arm/include/pthread_md.h b/lib/libthr/arch/arm/include/pthread_md.h
--- a/lib/libthr/arch/arm/include/pthread_md.h
+++ b/lib/libthr/arch/arm/include/pthread_md.h
@@ -50,4 +50,6 @@
 	return (NULL);
 }
 
+#define	_cfi_undefine_ra()
+
 #endif /* _PTHREAD_MD_H_ */
diff --git a/lib/libthr/arch/i386/include/pthread_md.h b/lib/libthr/arch/i386/include/pthread_md.h
--- a/lib/libthr/arch/i386/include/pthread_md.h
+++ b/lib/libthr/arch/i386/include/pthread_md.h
@@ -56,4 +56,6 @@
 
 #define HAS__UMTX_OP_ERR	1
 
+#define	_cfi_undefine_ra()	__asm __volatile(".cfi_undefined %eip")
+
 #endif
diff --git a/lib/libthr/arch/powerpc/include/pthread_md.h b/lib/libthr/arch/powerpc/include/pthread_md.h
--- a/lib/libthr/arch/powerpc/include/pthread_md.h
+++ b/lib/libthr/arch/powerpc/include/pthread_md.h
@@ -53,4 +53,6 @@
 
 #define	HAS__UMTX_OP_ERR	1
 
+#define	_cfi_undefine_ra()
+
 #endif /* _PTHREAD_MD_H_ */
diff --git a/lib/libthr/arch/riscv/include/pthread_md.h b/lib/libthr/arch/riscv/include/pthread_md.h
--- a/lib/libthr/arch/riscv/include/pthread_md.h
+++ b/lib/libthr/arch/riscv/include/pthread_md.h
@@ -58,4 +58,6 @@
 	return (NULL);
 }
 
+#define	_cfi_undefine_ra()	__asm __volatile(".cfi_undefined ra")
+
 #endif /* _PTHREAD_MD_H_ */
diff --git a/lib/libthr/thread/thr_create.c b/lib/libthr/thread/thr_create.c
--- a/lib/libthr/thread/thr_create.c
+++ b/lib/libthr/thread/thr_create.c
@@ -255,6 +255,8 @@
 {
 	sigset_t set;
 
+	_cfi_undefine_ra();
+
 	if (curthread->attr.suspend == THR_CREATE_SUSPENDED)
 		set = curthread->sigmask;
 	_thr_signal_block_setup(curthread);