diff --git a/asm/src/main/java/dev/openrs2/asm/InsnNodeUtils.java b/asm/src/main/java/dev/openrs2/asm/InsnNodeUtils.java
index 370a89a5..fdb8ea32 100644
--- a/asm/src/main/java/dev/openrs2/asm/InsnNodeUtils.java
+++ b/asm/src/main/java/dev/openrs2/asm/InsnNodeUtils.java
@@ -115,6 +115,7 @@ public final class InsnNodeUtils {
 	public static boolean hasSideEffects(AbstractInsnNode insn) {
 		var opcode = insn.getOpcode();
 		switch (opcode) {
+		case -1:
 		case Opcodes.NOP:
 		case Opcodes.ACONST_NULL:
 		case Opcodes.ICONST_M1:
diff --git a/asm/src/main/java/dev/openrs2/asm/StackMetadata.java b/asm/src/main/java/dev/openrs2/asm/StackMetadata.java
index e82897bc..12e5e1e0 100644
--- a/asm/src/main/java/dev/openrs2/asm/StackMetadata.java
+++ b/asm/src/main/java/dev/openrs2/asm/StackMetadata.java
@@ -32,6 +32,7 @@ public final class StackMetadata {
 	public static StackMetadata get(AbstractInsnNode insn) {
 		var opcode = insn.getOpcode();
 		switch (opcode) {
+		case -1:
 		case Opcodes.NOP:
 			return NONE;
 		case Opcodes.ACONST_NULL: