diff --git a/doc/source/mag.rst b/doc/source/mag.rst
index 841d5a31..e17caa01 100644
--- a/doc/source/mag.rst
+++ b/doc/source/mag.rst
@@ -165,6 +165,10 @@ Conversions
 
     Sets *y* exactly to *x*. Assumes that no overflow occurs.
 
+.. function:: double mag_get_d(const mag_t x)
+
+    Returns a *double* giving an upper bound for *x*.
+
 .. function:: void mag_set_ui_lower(mag_t z, ulong x)
 
 .. function:: void mag_set_fmpz_lower(mag_t z, const fmpz_t x)
diff --git a/mag.h b/mag.h
index 287b23fa..76086e0c 100644
--- a/mag.h
+++ b/mag.h
@@ -562,7 +562,6 @@ MAG_INLINE void mag_set_d(mag_t z, double x)
     fmpz_clear(e);
 }
 
-/* TODO: test/document */
 double mag_get_d(const mag_t z);
 
 /* TODO: document */
diff --git a/mag/test/t-get_d.c b/mag/test/t-get_d.c
new file mode 100644
index 00000000..272bb15f
--- /dev/null
+++ b/mag/test/t-get_d.c
@@ -0,0 +1,89 @@
+/*=============================================================================
+
+    This file is part of ARB.
+
+    ARB is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    ARB 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with ARB; if not, write to the Free Software
+    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+=============================================================================*/
+/******************************************************************************
+
+    Copyright (C) 2014 Fredrik Johansson
+
+******************************************************************************/
+
+#include "flint/double_extras.h"
+#include "mag.h"
+
+int main()
+{
+    slong iter;
+    flint_rand_t state;
+
+    flint_printf("get_d....");
+    fflush(stdout);
+
+    flint_randinit(state);
+
+    for (iter = 0; iter < 100000; iter++)
+    {
+        mag_t x;
+        fmpr_t a, b;
+        double y;
+
+        mag_init(x);
+        fmpr_init(a);
+        fmpr_init(b);
+
+        mag_randtest_special(x, state, 1 + n_randint(state, 100));
+
+        y = mag_get_d(x);
+        fmpr_set_d(a, y);
+
+        mag_get_fmpr(b, x);
+
+        if (mag_cmp_2exp_si(x, 1000) < 0 && mag_cmp_2exp_si(x, -1000) > 0)
+        {
+            if (!fmpr_equal(a, b))
+            {
+                flint_printf("FAIL (equality)\n\n");
+                flint_printf("x = "); mag_print(x); flint_printf("\n\n");
+                flint_printf("a = "); fmpr_print(a); flint_printf("\n\n");
+                flint_printf("b = "); fmpr_print(b); flint_printf("\n\n");
+                abort();
+            }
+        }
+        else
+        {
+            if (fmpr_cmp(a, b) < 0)
+            {
+                flint_printf("FAIL (bound)\n\n");
+                flint_printf("x = "); mag_print(x); flint_printf("\n\n");
+                flint_printf("a = "); fmpr_print(a); flint_printf("\n\n");
+                flint_printf("b = "); fmpr_print(b); flint_printf("\n\n");
+                abort();
+            }
+        }
+
+        fmpr_clear(a);
+        fmpr_clear(b);
+        mag_clear(x);
+    }
+
+    flint_randclear(state);
+    flint_cleanup();
+    flint_printf("PASS\n");
+    return EXIT_SUCCESS;
+}
+