diff --git a/de4dot.code/deobfuscators/Confuser/ConstantsDecrypter.cs b/de4dot.code/deobfuscators/Confuser/ConstantsDecrypter.cs
index 1b99c30a..039880b2 100644
--- a/de4dot.code/deobfuscators/Confuser/ConstantsDecrypter.cs
+++ b/de4dot.code/deobfuscators/Confuser/ConstantsDecrypter.cs
@@ -473,6 +473,8 @@ namespace de4dot.code.deobfuscators.Confuser {
 		}
 
 		int getDynamicEndIndex(int startIndex, VariableDefinition local) {
+			if (startIndex < 0)
+				return -1;
 			var instrs = installMethod.Body.Instructions;
 			for (int i = startIndex; i < instrs.Count; i++) {
 				var instr = instrs[i];