diff --git a/doc/meson.build b/doc/meson.build
index 8324708..37d515d 100644
--- a/doc/meson.build
+++ b/doc/meson.build
@@ -6,6 +6,7 @@ private_headers = [
   'aeslib.h',
   'assembling.h',
   'fp_internal.h',
+  'nbis-helpers.h',
   'fpi-async.h',
   'fpi-data.h',
 
diff --git a/libfprint/fp_internal.h b/libfprint/fp_internal.h
index d985738..5c89e18 100644
--- a/libfprint/fp_internal.h
+++ b/libfprint/fp_internal.h
@@ -27,6 +27,7 @@
 #include <glib.h>
 #include <libusb.h>
 
+#include "nbis-helpers.h"
 #include "fprint.h"
 #include "fpi-dev.h"
 #include "fpi-core.h"
diff --git a/libfprint/meson.build b/libfprint/meson.build
index ce761ba..abd0005 100644
--- a/libfprint/meson.build
+++ b/libfprint/meson.build
@@ -1,5 +1,6 @@
 libfprint_sources = [
     'fp_internal.h',
+    'nbis-helpers.h',
     'drivers_api.h',
     'fpi-async.c',
     'fpi-async.h',
diff --git a/libfprint/nbis-helpers.h b/libfprint/nbis-helpers.h
new file mode 100644
index 0000000..eab861e
--- /dev/null
+++ b/libfprint/nbis-helpers.h
@@ -0,0 +1,33 @@
+/*
+ * Helpers to use within the NBIS copy/paste library
+ * Copyright (C) 2018 Bastien Nocera <hadess@hadess.net>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <glib.h>
+
+#define ASSERT_SIZE_MUL(a,b)					\
+	{							\
+		gsize dest;					\
+		g_assert(g_size_checked_mul(&dest, a, b));	\
+	}
+
+#define ASSERT_INT_MUL(a, b)					\
+	{							\
+		gsize dest;					\
+		g_assert(g_size_checked_mul(&dest, a, b));	\
+		g_assert(dest < G_MAXINT);			\
+	}