diff --git a/asdf-core/src/main/java/org/asdfformat/asdf/node/impl/BooleanAsdfNode.java b/asdf-core/src/main/java/org/asdfformat/asdf/node/impl/BooleanAsdfNode.java
index 6048c0d..c2da6aa 100644
--- a/asdf-core/src/main/java/org/asdfformat/asdf/node/impl/BooleanAsdfNode.java
+++ b/asdf-core/src/main/java/org/asdfformat/asdf/node/impl/BooleanAsdfNode.java
@@ -52,7 +52,7 @@ public String getTag() {
     public boolean asBoolean() {
         final Boolean result = BOOLEAN_VALUES.get(value.toLowerCase());
         if (result == null) {
-            throw new RuntimeException(String.format("Unrecognized boolean value: %s", result));
+            throw new RuntimeException(String.format("Unrecognized boolean value: %s", value));
         }
         return result;
     }