diff --git a/src/main/java/li/cil/circuity/vm/riscv/R5CPU.java b/src/main/java/li/cil/circuity/vm/riscv/R5CPU.java
index e5f8f574..c8d7eaa7 100644
--- a/src/main/java/li/cil/circuity/vm/riscv/R5CPU.java
+++ b/src/main/java/li/cil/circuity/vm/riscv/R5CPU.java
@@ -1467,6 +1467,9 @@ public final class R5CPU implements Steppable, RealTimeCounter, InterruptControl
         if (priv == R5.PRIVILEGE_U) {
             throw new R5IllegalInstructionException(inst);
         }
+        if ((mstatus & R5.STATUS_TW_MASK) != 0 && priv == R5.PRIVILEGE_S) {
+            throw new R5IllegalInstructionException(inst);
+        }
 
         if ((mip.get() & mie) != 0) {
             return false;