diff --git a/compiler/src/test/scala/org/capnproto/EncodingTest.scala b/compiler/src/test/scala/org/capnproto/EncodingTest.scala
index 88f766a..3a30561 100644
--- a/compiler/src/test/scala/org/capnproto/EncodingTest.scala
+++ b/compiler/src/test/scala/org/capnproto/EncodingTest.scala
@@ -379,6 +379,12 @@ class EncodingSuite extends FunSuite {
     }
   }
 
+  test("TextBuilderIntUnderflow") {
+    val message = new MessageBuilder();
+    val root = message.initRoot(TestAnyPointer.factory);
+    root.getAnyPointerField.initAs(org.capnproto.Data.factory, 0);
+    a [DecodeException] should be thrownBy root.getAnyPointerField.getAs(org.capnproto.Text.factory);
+  }
 
   test("VoidListAmplification") {
     val builder = new MessageBuilder();
diff --git a/runtime/src/main/java/org/capnproto/WireHelpers.java b/runtime/src/main/java/org/capnproto/WireHelpers.java
index 25189de..e3a19a2 100644
--- a/runtime/src/main/java/org/capnproto/WireHelpers.java
+++ b/runtime/src/main/java/org/capnproto/WireHelpers.java
@@ -807,9 +807,13 @@ final class WireHelpers {
         }
 
 
-        //# Subtract 1 from the size for the NUL terminator.
+        int size = ListPointer.elementCount(resolved.ref);
+        if (size == 0 ||
+            resolved.segment.buffer.get(resolved.ptr * Constants.BYTES_PER_WORD + size - 1) != 0) {
+            throw new DecodeException("Text blob missing NUL terminator.");
+        }
         return new Text.Builder(resolved.segment.buffer, resolved.ptr * Constants.BYTES_PER_WORD,
-                                ListPointer.elementCount(resolved.ref) - 1);
+                                size - 1);
 
     }