diff --git a/doc/function/exists_in_package.txt b/doc/function/exists_in_package.txt
new file mode 100644
index 00000000..20f8d096
--- /dev/null
+++ b/doc/function/exists_in_package.txt
@@ -0,0 +1,13 @@
+Function: exists_in_package
+
+--Usage--
+> exists_in_package("/package/filename")
+
+Check if a file exists in a given package.
+
+--Parameters--
+! Parameter	Type			Description
+| @input@	[[type:string]]		Path of the file, starting from the data directory.
+
+--Examples--
+> exists_in_package("/magic-modules.mse-include/watermarks/custom_user_watermark.png")  ==  true
diff --git a/doc/function/index.txt b/doc/function/index.txt
index f0bfa889..13ed7844 100644
--- a/doc/function/index.txt
+++ b/doc/function/index.txt
@@ -113,3 +113,4 @@ These functions are built into the program, other [[type:function]]s can be defi
 | [[fun:assert]]		Check a condition for debugging purposes.
 | [[fun:warning]]		Output a warning message.
 | [[fun:error]]			Output an error message.
+| [[fun:exists_in_package]]			Checks if a file exists in a package.
diff --git a/src/script/functions/basic.cpp b/src/script/functions/basic.cpp
index ca00b002..c6b16795 100644
--- a/src/script/functions/basic.cpp
+++ b/src/script/functions/basic.cpp
@@ -13,6 +13,7 @@
 #include <util/tagged_string.hpp>
 #include <util/spec_sort.hpp>
 #include <util/error.hpp>
+#include <util/io/package_manager.hpp>
 #include <data/set.hpp>
 #include <data/card.hpp>
 #include <data/game.hpp>
@@ -62,7 +63,13 @@ SCRIPT_FUNCTION(error) {
     queue_message(MESSAGE_ERROR, input);
   }
   return script_nil;
-}
+}
+
+SCRIPT_FUNCTION(exists_in_package) {
+  SCRIPT_PARAM_C(String, input);
+  bool result = package_manager.existsInPackage(input);
+  SCRIPT_RETURN(result);
+}
 
 // ----------------------------------------------------------------------------- : Conversion
 
@@ -749,6 +756,7 @@ void init_script_basic_functions(Context& ctx) {
   ctx.setVariable(_("trace"),                script_trace);
   ctx.setVariable(_("warning"),              script_warning);
   ctx.setVariable(_("error"),                script_error);
+  ctx.setVariable(_("exists_in_package"),    script_exists_in_package);
   // conversion
   ctx.setVariable(_("to_string"),            script_to_string);
   ctx.setVariable(_("to_int"),               script_to_int);
diff --git a/src/util/io/package.cpp b/src/util/io/package.cpp
index b2384737..78df3cd8 100644
--- a/src/util/io/package.cpp
+++ b/src/util/io/package.cpp
@@ -186,6 +186,35 @@ public:
 
 // ----------------------------------------------------------------------------- : Package : inside
 
+bool Package::existsIn(const String& file) {
+  FileInfos::iterator it = files.find(normalize_internal_filename(file));
+  if (it == files.end()) {
+    // does it look like a relative filename?
+    if (filename.find(_(".mse-")) != String::npos) {
+      return false;
+    }
+  }
+
+  unique_ptr<wxInputStream> stream;
+  if (it != files.end() && it->second.wasWritten()) {
+    // written to this file, open the temp file
+    stream = make_unique<wxFileInputStream>(it->second.tempName);
+  }
+  else if (wxFileExists(filename + _("/") + file)) {
+    // a file in directory package
+    stream = make_unique<wxFileInputStream>(filename + _("/") + file);
+  }
+  else if (wxFileExists(filename) && it != files.end() && it->second.zipEntry) {
+    // a file in a zip archive
+    stream = make_unique<ZipFileInputStream>(filename, it->second.zipEntry);
+  }
+  else {
+    // shouldn't happen, packaged changed by someone else since opening it
+    return false;
+  }
+  return stream && stream->IsOk();
+}
+
 unique_ptr<wxInputStream> Package::openIn(const String& file) {
   if (!file.empty() && file.GetChar(0) == _('/')) {
     // absolute path, open file from another package
diff --git a/src/util/io/package.hpp b/src/util/io/package.hpp
index 6d15df9c..eee03149 100644
--- a/src/util/io/package.hpp
+++ b/src/util/io/package.hpp
@@ -132,10 +132,16 @@ public:
 
   // --------------------------------------------------- : Managing the inside of the package
 
+  /// Check if a file is in the package.
+  bool existsIn(const String& file);
+  inline bool existsIn(const LocalFileName& file) {
+      return existsIn(file.fn);
+  }
+
   /// Open an input stream for a file in the package.
   unique_ptr<wxInputStream> openIn(const String& file);
   inline unique_ptr<wxInputStream> openIn(const LocalFileName& file) {
-    return openIn(file.fn);
+      return openIn(file.fn);
   }
 
   /// Open an output stream for a file in the package.
diff --git a/src/util/io/package_manager.cpp b/src/util/io/package_manager.cpp
index 2f368ad0..9eeca4f2 100644
--- a/src/util/io/package_manager.cpp
+++ b/src/util/io/package_manager.cpp
@@ -95,6 +95,20 @@ void PackageManager::findMatching(const String& pattern, vector<PackagedP>& out)
   }
 }
 
+bool PackageManager::existsInPackage(const String& name) {
+  if (!name.empty() && name.GetChar(0) == _('/')) {
+    // break name
+    size_t start = name.find_first_not_of(_("/\\"), 1); // allow "//package/name" from incorrect scripts
+    size_t pos = name.find_first_of(_("/\\"), start);
+    if (start < pos && pos != String::npos) {
+      // open package
+      PackagedP p = openAny(name.substr(start, pos - start));
+      return p->existsIn(name.substr(pos + 1));
+    }
+  }
+  throw FileNotFoundError(name, _("No package name specified, use '/package/filename'"));
+}
+
 pair<unique_ptr<wxInputStream>,Packaged*> PackageManager::openFileFromPackage(Packaged* package, const String& name) {
   if (!name.empty() && name.GetChar(0) == _('/')) {
     // absolute name; break name
diff --git a/src/util/io/package_manager.hpp b/src/util/io/package_manager.hpp
index 4178d310..7e6037c4 100644
--- a/src/util/io/package_manager.hpp
+++ b/src/util/io/package_manager.hpp
@@ -139,7 +139,10 @@ public:
   /// Find all packages that match a filename pattern, store them in out
   /** Only reads the package headers */
   void findMatching(const String& pattern, vector<PackagedP>& out);
-  
+
+  /// Check if a file exists in a package
+  bool existsInPackage(const String& name);
+
   /// Open a file from a package, with a name encoded as "/package/file"
   /** If 'package' is set then:
    *    - tries to open a relative file from the package if the name is "file"
@@ -148,7 +151,7 @@ public:
    *  Returns the opened file and the package it is in
    */
   pair<unique_ptr<wxInputStream>,Packaged*> openFileFromPackage(Packaged* package, const String& name);
-  
+
   /// Get a filename to open from a package
   /** WARNING: this is a bit of a hack, since not all package types support names in this way.
    *  It is needed for third party libraries (i.e. hunspell) that load stuff from files.
diff --git a/tools/website/drupal/mse-drupal-modules/highlight.inc b/tools/website/drupal/mse-drupal-modules/highlight.inc
index afe0b0d7..2c9f908d 100644
--- a/tools/website/drupal/mse-drupal-modules/highlight.inc
+++ b/tools/website/drupal/mse-drupal-modules/highlight.inc
@@ -102,6 +102,7 @@ $built_in_functions = array(
 	// other
 	'trace'			=>'',
 	'assert'		=>'',
+	'exists_in_package'		=>'',
 );