diff --git a/model/riscv_insts_aext.sail b/model/riscv_insts_aext.sail
index 00bf0d10b..3bf44b8f5 100644
--- a/model/riscv_insts_aext.sail
+++ b/model/riscv_insts_aext.sail
@@ -43,8 +43,8 @@ function amo_width_valid(size : word_width) -> bool = {
 /* ****************************************************************** */
 union clause ast = LOADRES : (bool, bool, regidx, word_width, regidx)
 
-mapping clause encdec = LOADRES(aq, rl, rs1, size, rd)                                                if haveAtomics() & amo_width_valid(size)
-  <-> 0b00010 @ bool_bits(aq) @ bool_bits(rl) @ 0b00000 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveAtomics() & amo_width_valid(size)
+mapping clause encdec = LOADRES(aq, rl, rs1, size, rd)                                                if haveZalrsc() & amo_width_valid(size)
+  <-> 0b00010 @ bool_bits(aq) @ bool_bits(rl) @ 0b00000 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveZalrsc() & amo_width_valid(size)
 
 
 /* We could set load-reservations on physical or virtual addresses.
@@ -88,8 +88,8 @@ mapping clause assembly = LOADRES(aq, rl, rs1, size, rd)
 /* ****************************************************************** */
 union clause ast = STORECON : (bool, bool, regidx, regidx, word_width, regidx)
 
-mapping clause encdec = STORECON(aq, rl, rs2, rs1, size, rd)                                      if haveAtomics() & amo_width_valid(size)
-  <-> 0b00011 @ bool_bits(aq) @ bool_bits(rl) @ rs2 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveAtomics() & amo_width_valid(size)
+mapping clause encdec = STORECON(aq, rl, rs2, rs1, size, rd)                                      if haveZalrsc() & amo_width_valid(size)
+  <-> 0b00011 @ bool_bits(aq) @ bool_bits(rl) @ rs2 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveZalrsc() & amo_width_valid(size)
 
 /* NOTE: Currently, we only EA if address translation is successful. This may need revisiting. */
 function clause execute (STORECON(aq, rl, rs2, rs1, width, rd)) = {
@@ -163,8 +163,8 @@ mapping encdec_amoop : amoop <-> bits(5) = {
   AMOMAXU <-> 0b11100
 }
 
-mapping clause encdec = AMO(op, aq, rl, rs2, rs1, size, rd)                                                if haveAtomics() & amo_width_valid(size)
-  <-> encdec_amoop(op) @ bool_bits(aq) @ bool_bits(rl) @ rs2 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveAtomics() & amo_width_valid(size)
+mapping clause encdec = AMO(op, aq, rl, rs2, rs1, size, rd)                                                if haveZaamo() & amo_width_valid(size)
+  <-> encdec_amoop(op) @ bool_bits(aq) @ bool_bits(rl) @ rs2 @ rs1 @ 0b0 @ size_enc(size) @ rd @ 0b0101111 if haveZaamo() & amo_width_valid(size)
 
 /* NOTE: Currently, we only EA if address translation is successful.
    This may need revisiting. */
diff --git a/model/riscv_sys_regs.sail b/model/riscv_sys_regs.sail
index 6c66492b4..3537abc16 100644
--- a/model/riscv_sys_regs.sail
+++ b/model/riscv_sys_regs.sail
@@ -161,6 +161,10 @@ function haveZknd()   -> bool = true
 
 function haveZmmul()  -> bool = true
 
+/* A extension sub-extensions */
+function haveZaamo()  -> bool = haveAtomics()
+function haveZalrsc() -> bool = haveAtomics()
+
 /* Zicond extension support */
 function haveZicond() -> bool = true