diff --git a/README.md b/README.md
index 2c5bba9145..6d898d9546 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,7 @@ Spike supports the following RISC-V ISA features:
   - Smepmp extension v1.0
   - Smstateen extension, v1.0
   - Sscofpmf v0.5.2
+  - Ssdtso v1.0
   - Zca extension, v1.0
   - Zcb extension, v1.0
   - Zcf extension, v1.0
diff --git a/disasm/isa_parser.cc b/disasm/isa_parser.cc
index ef513108d1..2760b35019 100644
--- a/disasm/isa_parser.cc
+++ b/disasm/isa_parser.cc
@@ -292,6 +292,8 @@ isa_parser_t::isa_parser_t(const char* str, const char *priv)
       extension_table[EXT_SMCSRIND] = true;
     } else if (ext_str == "sscsrind") {
       extension_table[EXT_SSCSRIND] = true;
+    } else if (ext_str == "ssdtso") {
+      extension_table[EXT_SSDTSO] = true;
     } else if (ext_str == "smcntrpmf") {
       extension_table[EXT_SMCNTRPMF] = true;
     } else if (ext_str == "zcmop") {
diff --git a/riscv/encoding.h b/riscv/encoding.h
index 81d829cf15..2bf43c15db 100644
--- a/riscv/encoding.h
+++ b/riscv/encoding.h
@@ -160,6 +160,7 @@
 #define MENVCFG_CBIE  0x00000030
 #define MENVCFG_CBCFE 0x00000040
 #define MENVCFG_CBZE  0x00000080
+#define MENVCFG_DTSO  0x00000100
 #define MENVCFG_ADUE  0x2000000000000000
 #define MENVCFG_PBMTE 0x4000000000000000
 #define MENVCFG_STCE  0x8000000000000000
@@ -198,6 +199,7 @@
 #define HENVCFG_CBIE  0x00000030
 #define HENVCFG_CBCFE 0x00000040
 #define HENVCFG_CBZE  0x00000080
+#define HENVCFG_DTSO  0x00000100
 #define HENVCFG_ADUE  0x2000000000000000
 #define HENVCFG_PBMTE 0x4000000000000000
 #define HENVCFG_STCE  0x8000000000000000
@@ -233,6 +235,7 @@
 #define SENVCFG_CBIE  0x00000030
 #define SENVCFG_CBCFE 0x00000040
 #define SENVCFG_CBZE  0x00000080
+#define SENVCFG_DTSO  0x00000100
 
 #define SSTATEEN0_CS   0x00000001
 #define SSTATEEN0_FCSR 0x00000002
diff --git a/riscv/isa_parser.h b/riscv/isa_parser.h
index a84b6fe8d7..f91cf67f78 100644
--- a/riscv/isa_parser.h
+++ b/riscv/isa_parser.h
@@ -80,6 +80,7 @@ typedef enum {
   EXT_INTERNAL_ZFH_MOVE,
   EXT_SMCSRIND,
   EXT_SSCSRIND,
+  EXT_SSDTSO,
   EXT_SMCNTRPMF,
   EXT_ZCMOP,
   EXT_ZALASR,