diff --git a/ts2panda/src/debuginfo.ts b/ts2panda/src/debuginfo.ts
index b49a58105a3a0e58a2819681e6984fdf8fd01110..7e95232598f43762bf4c96f32041774cf20cba93 100644
--- a/ts2panda/src/debuginfo.ts
+++ b/ts2panda/src/debuginfo.ts
@@ -309,13 +309,17 @@ export class DebugInfo {
                 (<DebugInsStartPlaceHolder> insns[i]).getScope().setScopeStartInsIdx(i);
                 // delete ins placeholder
                 insns.splice(i, 1);
-                i--;
+                if (i > 0) {
+                    i--;
+                }
             }
             if (insns[i] instanceof DebugInsEndPlaceHolder) {
-                (<DebugInsEndPlaceHolder> insns[i]).getScope().setScopeEndInsIdx(i);
+                (<DebugInsEndPlaceHolder> insns[i]).getScope().setScopeEndInsIdx(i > 0 ? i - 1 : 0);
                 // delete ins placeholder
                 insns.splice(i, 1);
-                i--;
+                if (i > 0) {
+                    i--;
+                }
             }
         }