diff --git a/lib/libsysdecode/flags.c b/lib/libsysdecode/flags.c
index 1eb48858fd88..df461cf0dca1 100644
--- a/lib/libsysdecode/flags.c
+++ b/lib/libsysdecode/flags.c
@@ -941,6 +941,20 @@ sysdecode_umtx_op(int op)
 	return (lookup_value(umtxop, op));
 }
 
+bool
+sysdecode_umtx_op_flags(FILE *fp, int op, int *rem)
+{
+	uintmax_t val;
+	bool printed;
+
+	printed = false;
+	val = (unsigned)op;
+	print_mask_part(fp, umtxopflags, &val, &printed);
+	if (rem != NULL)
+		*rem = val;
+	return (printed);
+}
+
 const char *
 sysdecode_vmresult(int result)
 {
diff --git a/lib/libsysdecode/mktables b/lib/libsysdecode/mktables
index b42978d57c4d..3a0284a2deb4 100644
--- a/lib/libsysdecode/mktables
+++ b/lib/libsysdecode/mktables
@@ -145,7 +145,8 @@ gen_table "sockoptudp"      "UDP_[[:alnum:]]+[[:space:]]+[0-9]+"           "neti
 gen_table "sockoptudplite"  "UDPLITE_[[:alnum:]_]+[[:space:]]+[0-9]+"      "netinet/udplite.h"
 gen_table "socktype"        "SOCK_[A-Z]+[[:space:]]+[1-9]+[0-9]*"          "sys/socket.h"
 gen_table "thrcreateflags"  "THR_[A-Z]+[[:space:]]+0x[0-9]+"               "sys/thr.h"
-gen_table "umtxop"          "UMTX_OP_[[:alnum:]_]+[[:space:]]+[0-9]+"      "sys/umtx.h"
+gen_table "umtxop"          "UMTX_OP_[[:alnum:]][[:alnum:]_]*[[:space:]]+[0-9]+"      "sys/umtx.h"
+gen_table "umtxopflags"     "UMTX_OP__[[:alnum:]_]+[[:space:]]+[0-9]+"                "sys/umtx.h"
 gen_table "vmprot"          "VM_PROT_[A-Z]+[[:space:]]+\(\(vm_prot_t\)[[:space:]]+0x[0-9]+\)"  "vm/vm.h"
 gen_table "vmresult"        "KERN_[A-Z_]+[[:space:]]+[0-9]+"               "vm/vm_param.h"
 gen_table "wait6opt"        "W[A-Z]+[[:space:]]+[0-9]+"                    "sys/wait.h"
diff --git a/lib/libsysdecode/sysdecode.h b/lib/libsysdecode/sysdecode.h
index a01ac1243aa2..cdb9205f3da1 100644
--- a/lib/libsysdecode/sysdecode.h
+++ b/lib/libsysdecode/sysdecode.h
@@ -121,6 +121,7 @@ const char *sysdecode_sysarch_number(int _number);
 bool	sysdecode_thr_create_flags(FILE *_fp, int _flags, int *_rem);
 bool	sysdecode_umtx_cvwait_flags(FILE *_fp, u_long _flags, u_long *_rem);
 const char *sysdecode_umtx_op(int _op);
+bool	sysdecode_umtx_op_flags(FILE *_fp, int op, int *_rem);
 bool	sysdecode_umtx_rwlock_flags(FILE *_fp, u_long _flags, u_long *_rem);
 int	sysdecode_utrace(FILE *_fp, void *_buf, size_t _len);
 bool	sysdecode_vmprot(FILE *_fp, int _type, int *_rem);