diff --git a/src/main/java/com/amazon/ion/impl/IonReaderTextSystemX.java b/src/main/java/com/amazon/ion/impl/IonReaderTextSystemX.java
index edf4431936..713422d44b 100644
--- a/src/main/java/com/amazon/ion/impl/IonReaderTextSystemX.java
+++ b/src/main/java/com/amazon/ion/impl/IonReaderTextSystemX.java
@@ -606,9 +606,7 @@ public final String stringValue()
         load_or_cast_cached_value(AS_TYPE.string_value);
         String text = _v.getString();
         if (text == null) {
-            assert _value_type == IonType.SYMBOL;
             int sid = _v.getInt();
-            assert sid > 0;
             throw new UnknownSymbolException(sid);
         }
         return text;
diff --git a/src/test/java/com/amazon/ion/streaming/ReaderTest.java b/src/test/java/com/amazon/ion/streaming/ReaderTest.java
index 65eebcf87b..88ccc42f54 100644
--- a/src/test/java/com/amazon/ion/streaming/ReaderTest.java
+++ b/src/test/java/com/amazon/ion/streaming/ReaderTest.java
@@ -25,6 +25,7 @@
 import com.amazon.ion.ReaderMaker;
 import com.amazon.ion.SymbolTable;
 import com.amazon.ion.SymbolToken;
+import com.amazon.ion.UnknownSymbolException;
 import com.amazon.ion.junit.Injected.Inject;
 import com.amazon.ion.junit.IonAssert;
 import java.io.IOException;
@@ -193,6 +194,14 @@ public void testStringValueOnNonText()
         }
     }
 
+    @Test
+    public void testStringValueOnSymbolWithUndefinedText()
+    {
+        read("$0");
+        assertEquals(IonType.SYMBOL, in.next());
+        assertThrows(UnknownSymbolException.class, () -> in.stringValue());
+    }
+
     @Test
     public void testSymbolValue()
         throws Exception