diff --git a/source/dub/project.d b/source/dub/project.d
index 134ca2c..b433b25 100644
--- a/source/dub/project.d
+++ b/source/dub/project.d
@@ -266,15 +266,9 @@
 		const config = format("%s-test-%s", rootPackage.name.replace(".", "-").replace(":", "-"), base_config);
 		logInfo(`Generating test runner configuration '%s' for '%s' (%s).`, config, base_config, lbuildsettings.targetType);
 
-		BuildSettingsTemplate tcinfo = rootPackage.recipe.getConfiguration(base_config).buildSettings;
+		BuildSettingsTemplate tcinfo = rootPackage.recipe.getConfiguration(base_config).buildSettings.dup;
 		tcinfo.targetType = TargetType.executable;
 
-		// AAs in tcinfo need to be dup'd to avoid modifying the base config's buildSettings too
-		static void appendToDefaultAAEntry(ref string[][string] aa, string entry) {
-			aa = aa.dup;
-			aa[""] ~= entry;
-		}
-
 		// set targetName unless specified explicitly in unittest base configuration
 		if (tcinfo.targetName.empty || base_config != "unittest")
 			tcinfo.targetName = config;
@@ -285,8 +279,8 @@
 		string custommodname;
 		if (!custom_main_file.empty) {
 			import std.path;
-			appendToDefaultAAEntry(tcinfo.sourceFiles, custom_main_file.relativeTo(rootPackage.path).toNativeString());
-			appendToDefaultAAEntry(tcinfo.importPaths, custom_main_file.parentPath.toNativeString());
+			tcinfo.sourceFiles[""] ~= custom_main_file.relativeTo(rootPackage.path).toNativeString();
+			tcinfo.importPaths[""] ~= custom_main_file.parentPath.toNativeString();
 			custommodname = custom_main_file.head.name.baseName(".d");
 		}
 
@@ -304,7 +298,7 @@
 					msf = msf.relativeTo(rootPackage.path);
 				if (!settings.single && NativePath(file).relativeTo(rootPackage.path) == msf) {
 					logWarn("Excluding main source file %s from test.", mainfil);
-					appendToDefaultAAEntry(tcinfo.excludedSourceFiles, mainfil);
+					tcinfo.excludedSourceFiles[""] ~= mainfil;
 					continue;
 				}
 				if (fname == "package.d") {
@@ -327,11 +321,11 @@
 		}
 
 		auto escapedMainFile = mainfile.toNativeString().replace("$", "$$");
-		appendToDefaultAAEntry(tcinfo.sourceFiles, escapedMainFile);
+		tcinfo.sourceFiles[""] ~= escapedMainFile;
 		tcinfo.mainSourceFile = escapedMainFile;
 		if (!settings.tempBuild) {
 			// add the directory containing dub_test_root.d to the import paths
-			appendToDefaultAAEntry(tcinfo.importPaths, NativePath(escapedMainFile).parentPath.toNativeString());
+			tcinfo.importPaths[""] ~= NativePath(escapedMainFile).parentPath.toNativeString();
 		}
 
 		if (generate_main && (settings.force || !existsFile(mainfile))) {
diff --git a/source/dub/recipe/packagerecipe.d b/source/dub/recipe/packagerecipe.d
index d7ed15b..33bf25c 100644
--- a/source/dub/recipe/packagerecipe.d
+++ b/source/dub/recipe/packagerecipe.d
@@ -218,6 +218,10 @@
 	Flags!BuildOption[string] buildOptions;
 
 
+	BuildSettingsTemplate dup() const {
+		return clone(this);
+	}
+
 	/// Constructs a BuildSettings object from this template.
 	void getPlatformSettings(ref BuildSettings dst, in BuildPlatform platform, NativePath base_path)
 	const {