diff --git a/zjit/src/backend/lir.rs b/zjit/src/backend/lir.rs
index a0065b574c..e4d00fea7b 100644
--- a/zjit/src/backend/lir.rs
+++ b/zjit/src/backend/lir.rs
@@ -1683,6 +1683,7 @@ impl Assembler {
     }
 
     pub fn cpop_into(&mut self, opnd: Opnd) {
+        assert!(matches!(opnd, Opnd::Reg(_)), "Destination of cpop_into must be a register, got: {opnd:?}");
         self.push_insn(Insn::CPopInto(opnd));
     }
 
@@ -1830,6 +1831,7 @@ impl Assembler {
     }
 
     pub fn lea_into(&mut self, out: Opnd, opnd: Opnd) {
+        assert!(matches!(out, Opnd::Reg(_)), "Destination of lea_into must be a register, got: {out:?}");
         self.push_insn(Insn::Lea { opnd, out });
     }
 
@@ -1855,7 +1857,7 @@ impl Assembler {
     }
 
     pub fn load_into(&mut self, dest: Opnd, opnd: Opnd) {
-        assert!(matches!(dest, Opnd::Reg(_) | Opnd::VReg{..}), "Destination of load_into must be a register");
+        assert!(matches!(dest, Opnd::Reg(_)), "Destination of load_into must be a register, got: {dest:?}");
         match (dest, opnd) {
             (Opnd::Reg(dest), Opnd::Reg(opnd)) if dest == opnd => {}, // skip if noop
             _ => self.push_insn(Insn::LoadInto { dest, opnd }),
@@ -1881,6 +1883,7 @@ impl Assembler {
     }
 
     pub fn mov(&mut self, dest: Opnd, src: Opnd) {
+        assert!(!matches!(dest, Opnd::VReg { .. }), "Destination of mov must not be Opnd::VReg, got: {dest:?}");
         self.push_insn(Insn::Mov { dest, src });
     }
 
@@ -1918,6 +1921,7 @@ impl Assembler {
     }
 
     pub fn store(&mut self, dest: Opnd, src: Opnd) {
+        assert!(!matches!(dest, Opnd::VReg { .. }), "Destination of store must not be Opnd::VReg, got: {dest:?}");
         self.push_insn(Insn::Store { dest, src });
     }