diff --git a/model_checking/sail_decoder/lib.rs b/model_checking/sail_decoder/lib.rs
index 7e27d8ca..374578de 100644
--- a/model_checking/sail_decoder/lib.rs
+++ b/model_checking/sail_decoder/lib.rs
@@ -101,12 +101,6 @@ pub fn encdec_backwards(sail_ctx: &mut SailVirtCtx, arg_hashtag_: BitVector<32>)
             v__7 if { (v__7 == BitVector::<32>::new(0b00010000010100000000000001110011)) } => {
                 ast::WFI(())
             }
-            v__13 if { (v__13 == BitVector::<32>::new(0b00000000000000000000000001110011)) } => {
-                ast::ECALL(())
-            }
-            v__19 if { (v__19 == BitVector::<32>::new(0b00000000000100000000000001110011)) } => {
-                ast::EBREAK(())
-            }
             v__25
                 if {
                     ((v__25.subrange::<25, 32, 7>() == BitVector::<7>::new(0b0001001))
diff --git a/model_checking/src/adapters.rs b/model_checking/src/adapters.rs
index 2812d999..cf43ca26 100644
--- a/model_checking/src/adapters.rs
+++ b/model_checking/src/adapters.rs
@@ -447,8 +447,8 @@ pub fn ast_to_miralis_instr(ast_entry: ast) -> Instr {
     match ast_entry {
         ast::MRET(()) => Instr::Mret,
         ast::WFI(()) => Instr::Wfi,
-        ast::ECALL(()) => Instr::Ecall,
-        ast::EBREAK(()) => Instr::Ebreak,
+        ast::ECALL(()) => panic!("Miralis does not need to decode ecalls"),
+        ast::EBREAK(()) => panic!("Miralis does not need to decode ebreaks"),
         ast::SFENCE_VMA((rs1, rs2)) => Instr::Sfencevma {
             rs1: Register::from(rs1.bits as usize),
             rs2: Register::from(rs2.bits as usize),
diff --git a/src/decoder.rs b/src/decoder.rs
index 15502f8d..4f93ba3b 100644
--- a/src/decoder.rs
+++ b/src/decoder.rs
@@ -6,8 +6,6 @@ use crate::logger;
 /// A RISC-V instruction.
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Instr {
-    Ecall,
-    Ebreak,
     Wfi,
     /// CSR Read/Write
     Csrrw {
@@ -110,8 +108,6 @@ impl MiralisContext {
         let func7 = (raw >> 25) & 0b1111111;
         if func3 == 0b000 {
             return match imm {
-                0b000000000000 => Instr::Ecall,
-                0b000000000001 => Instr::Ebreak,
                 0b000100000101 => Instr::Wfi,
                 0b001100000010 => Instr::Mret,
                 0b000100000010 => Instr::Sret,
@@ -872,10 +868,6 @@ mod tests {
     #[test]
     fn system_instructions() {
         let mctx = MiralisContext::new(unsafe { Arch::detect_hardware() }, 0x100000, 0x2000);
-        // ECALL: Environment call.
-        assert_eq!(mctx.decode_illegal_instruction(0x00000073), Instr::Ecall);
-        // EBREAK: Environment break.
-        assert_eq!(mctx.decode_illegal_instruction(0x00100073), Instr::Ebreak);
         // MRET: Return from machine mode.
         assert_eq!(mctx.decode_illegal_instruction(0x30200073), Instr::Mret);
         // SRET: Return from supervisor mode.