diff --git a/src/vm.cpp b/src/vm.cpp
index cd7c884..313b7bc 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -263,6 +263,13 @@ void VM::step() {
         } else {
           throw std::runtime_error("Unknown I-type instruction");
         }
+      } else if (funct3 == 0x02) {  // SLTI
+        setreg(rd, (static_cast<int32_t>(registers[rs1]) <
+                    static_cast<int32_t>(imm))
+                       ? 0
+                       : 1);
+      } else if (funct3 == 0x03) {  // SLTIU
+        setreg(rd, (registers[rs1] < static_cast<uint32_t>(imm)) ? 1 : 0);
       } else {
         throw std::runtime_error("Unknown I-type instruction");
       }