diff --git a/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java b/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java
index bbad1ca7bcbc..009ef8ff3dff 100644
--- a/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java
+++ b/core/src/main/java/org/apache/calcite/sql/type/SqlTypeUtil.java
@@ -1202,6 +1202,9 @@ public static boolean equalSansNullability(
    * @return true if the types are equal or the only difference is nullability
    */
   public static boolean equalSansNullability(RelDataType type1, RelDataType type2) {
+    if (type1 == type2) {
+      return true;
+    }
     String x = type1.getFullTypeString();
     String y = type2.getFullTypeString();
     if (x.length() < y.length()) {