diff --git a/CMakeLists.txt b/CMakeLists.txt
index 106f23ab..e1208a9a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -178,6 +178,7 @@ set(INTERNAL_HEADERS
         ${HEADER_DIR}/internal/catch_timer.h
         ${HEADER_DIR}/internal/catch_tostring.h
         ${HEADER_DIR}/internal/catch_totals.h
+        ${HEADER_DIR}/internal/catch_user_interfaces.h
         ${HEADER_DIR}/internal/catch_version.h
         ${HEADER_DIR}/internal/catch_wildcard_pattern.h
         ${HEADER_DIR}/internal/catch_windows_h_proxy.h
diff --git a/include/catch.hpp b/include/catch.hpp
index 8294f404..34c551be 100644
--- a/include/catch.hpp
+++ b/include/catch.hpp
@@ -43,6 +43,7 @@
 #  endif
 #endif
 
+#include "internal/catch_user_interfaces.h"
 #include "internal/catch_tag_alias_autoregistrar.h"
 #include "internal/catch_test_registry.h"
 #include "internal/catch_capture.hpp"
diff --git a/include/internal/catch_user_interfaces.h b/include/internal/catch_user_interfaces.h
new file mode 100644
index 00000000..35acb77b
--- /dev/null
+++ b/include/internal/catch_user_interfaces.h
@@ -0,0 +1,18 @@
+/*
+ *  Created by Martin on 21/11/2017.
+ *
+ *  This file collects declaration that we want to expose to test files.
+ *  These declarations are expected to be duplicated elsewhere,
+ *  together with their implementation.
+ *
+ *  Distributed under the Boost Software License, Version 1.0. (See accompanying
+ *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+#ifndef TWOBLUECUBES_CATCH_USER_INTERFACES_H_INCLUDED
+#define TWOBLUECUBES_CATCH_USER_INTERFACES_H_INCLUDED
+
+namespace Catch {
+    unsigned int rngSeed();
+}
+
+#endif // TWOBLUECUBES_CATCH_USER_INTERFACES_H_INCLUDED