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compiler/noirc_evaluator/src/ssa/ir/instruction/call.rs

@@ -402,6 +402,15 @@ fn simplify_slice_push_back(
     let len_equals_capacity = dfg
         .insert_instruction_and_results(len_equals_capacity_instr, block, None, call_stack.clone())
         .first();
+    let len_not_equals_capacity_instr = Instruction::Not(len_equals_capacity);
+    let len_not_equals_capacity = dfg
+        .insert_instruction_and_results(
+            len_not_equals_capacity_instr,
+            block,
+            None,
+            call_stack.clone(),
+        )
+        .first();
 
     let new_slice_length = update_slice_length(arguments[0], dfg, BinaryOp::Add, block);
 
@@ -431,7 +440,7 @@ fn simplify_slice_push_back(
     let mut value_merger =
         ValueMerger::new(dfg, block, &mut slice_sizes, unknown, None, call_stack);
 
-    let new_slice = value_merger.merge_values(len_equals_capacity, new_slice, set_last_slice_value);
+    let new_slice = value_merger.merge_values(len_not_equals_capacity, set_last_slice_value, new_slice);
 
     SimplifyResult::SimplifiedToMultiple(vec![new_slice_length, new_slice])
 }