diff --git a/src/libutil/json.cc b/src/libutil/json.cc
index 0a6fb65f0..74e37b4c4 100644
--- a/src/libutil/json.cc
+++ b/src/libutil/json.cc
@@ -171,4 +171,9 @@ JSONObject JSONPlaceholder::object()
     return JSONObject(state);
 }
 
+JSONPlaceholder::~JSONPlaceholder()
+{
+    assert(!first || std::uncaught_exception());
+}
+
 }
diff --git a/src/libutil/json.hh b/src/libutil/json.hh
index 02a39917f..83213ca66 100644
--- a/src/libutil/json.hh
+++ b/src/libutil/json.hh
@@ -168,10 +168,7 @@ public:
     {
     }
 
-    ~JSONPlaceholder()
-    {
-        assert(!first || std::uncaught_exception());
-    }
+    ~JSONPlaceholder();
 
     template<typename T>
     void write(const T & v)