diff --git a/panda/src/pgraph/paramNodePath.I b/panda/src/pgraph/paramNodePath.I
index 354a2af7ec..67a9d24ea6 100644
--- a/panda/src/pgraph/paramNodePath.I
+++ b/panda/src/pgraph/paramNodePath.I
@@ -11,24 +11,6 @@
  * @date 2015-02-25
  */
 
-/**
- * Creates a new ParamNodePath storing the given node path object.
- */
-INLINE ParamNodePath::
-ParamNodePath(const NodePath &node_path) :
-  _node_path(node_path)
-{
-}
-
-/**
- * Creates a new ParamNodePath storing the given node path object.
- */
-INLINE ParamNodePath::
-ParamNodePath(NodePath &&node_path) noexcept :
-  _node_path(std::move(node_path))
-{
-}
-
 /**
  * Returns NodePath::get_class_type().
  */
diff --git a/panda/src/pgraph/paramNodePath.cxx b/panda/src/pgraph/paramNodePath.cxx
index 72a3563b22..45bfe0c12f 100644
--- a/panda/src/pgraph/paramNodePath.cxx
+++ b/panda/src/pgraph/paramNodePath.cxx
@@ -14,9 +14,41 @@
 #include "paramNodePath.h"
 #include "dcast.h"
 #include "pandaNode.h"
+#include "light.h"
 
 TypeHandle ParamNodePath::_type_handle;
 
+/**
+ * Creates a new ParamNodePath storing the given node path object.
+ */
+ParamNodePath::
+ParamNodePath(NodePath node_path) :
+  _node_path(std::move(node_path))
+{
+  // The reason to construct a ParamNodePath is often to apply a light to a
+  // shader input, so we want to keep track of the fact that the light is in
+  // use.
+  if (!_node_path.is_empty()) {
+    Light *light = _node_path.node()->as_light();
+    if (light != nullptr) {
+      light->attrib_ref();
+    }
+  }
+}
+
+/**
+ *
+ */
+ParamNodePath::
+~ParamNodePath() {
+  if (!_node_path.is_empty()) {
+    Light *light = _node_path.node()->as_light();
+    if (light != nullptr) {
+      light->attrib_unref();
+    }
+  }
+}
+
 /**
  *
  */
@@ -68,6 +100,13 @@ complete_pointers(TypedWritable **p_list, BamReader *manager) {
     _node_path = NodePath(DCAST(PandaNode, p_list[pi++]));
   }
 
+  if (!_node_path.is_empty()) {
+    Light *light = _node_path.node()->as_light();
+    if (light != nullptr) {
+      light->attrib_ref();
+    }
+  }
+
   return pi;
 }
 
@@ -96,6 +135,14 @@ void ParamNodePath::
 fillin(DatagramIterator &scan, BamReader *manager) {
   ParamValueBase::fillin(scan, manager);
 
+  if (!_node_path.is_empty()) {
+    Light *light = _node_path.node()->as_light();
+    if (light != nullptr) {
+      light->attrib_unref();
+    }
+    _node_path.clear();
+  }
+
   if (manager->get_file_minor_ver() >= 40) {
     _node_path.fillin(scan, manager);
   } else {
diff --git a/panda/src/pgraph/paramNodePath.h b/panda/src/pgraph/paramNodePath.h
index daab53e41e..63798cc4a8 100644
--- a/panda/src/pgraph/paramNodePath.h
+++ b/panda/src/pgraph/paramNodePath.h
@@ -26,8 +26,8 @@ protected:
   INLINE ParamNodePath() {};
 
 PUBLISHED:
-  INLINE ParamNodePath(const NodePath &node_path);
-  INLINE ParamNodePath(NodePath &&node_path) noexcept;
+  ParamNodePath(NodePath node_path);
+  virtual ~ParamNodePath();
 
   INLINE virtual TypeHandle get_value_type() const;
   INLINE NodePath get_value() const;