diff --git a/core/src/main/java/org/lflang/analyses/pretvm/profiles/FlexPRETProfile.java b/core/src/main/java/org/lflang/analyses/pretvm/profiles/FlexPRETProfile.java
index 08ff6e64bb..1fa3bdfdcb 100644
--- a/core/src/main/java/org/lflang/analyses/pretvm/profiles/FlexPRETProfile.java
+++ b/core/src/main/java/org/lflang/analyses/pretvm/profiles/FlexPRETProfile.java
@@ -22,6 +22,7 @@ public static TimeValue getInstWCET(Opcode opcode) {
       case STP -> TimeValue.fromNanoSeconds(320L);
       case WLT -> TimeValue.fromNanoSeconds(400L);
       case WU -> TimeValue.fromNanoSeconds(400L);
+      default -> throw new IllegalArgumentException("Unknown opcode: " + opcode);
     };
   }
 }