diff --git a/src/main/java/com/android/tools/r8/ir/optimize/string/StringBuilderEscapeTransferFunction.java b/src/main/java/com/android/tools/r8/ir/optimize/string/StringBuilderEscapeTransferFunction.java
index 2ea5a08..bc92a0f 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/string/StringBuilderEscapeTransferFunction.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/string/StringBuilderEscapeTransferFunction.java
@@ -68,7 +68,7 @@
         if (!builder.getLiveStringBuilders().contains(firstOperand)) {
           // We can have constant NULL being the first operand, which we have not marked as
           // a live string builder.
-          assert firstOperand.isConstZero();
+          assert firstOperand.getAliasedValue().isConstZero();
           builder.addLiveStringBuilder(firstOperand);
         }
       } else {