diff --git a/ChangeLog b/ChangeLog
index a448acc4e..85e7a060f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,8 @@ PolarSSL ChangeLog
 Bugfixes
    * Fixes for MSVC6
    * Moved mpi_inv_mod() outside POLARSSL_GENPRIME
+   * Allow R and A to point to same mpi in mpi_div_mpi (found by Manuel
+     Pégourié-Gonnard)
 
 = Version 1.2.0 released 2012-10-31
 Features
diff --git a/library/bignum.c b/library/bignum.c
index 94e8eb3e2..23feb6a91 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1195,9 +1195,9 @@ int mpi_div_mpi( mpi *Q, mpi *R, const mpi *A, const mpi *B )
     if( R != NULL )
     {
         mpi_shift_r( &X, k );
+        X.s = A->s;
         mpi_copy( R, &X );
 
-        R->s = A->s;
         if( mpi_cmp_int( R, 0 ) == 0 )
             R->s = 1;
     }
diff --git a/tests/suites/test_suite_mpi.function b/tests/suites/test_suite_mpi.function
index 1b328c43d..663539259 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -514,21 +514,21 @@ END_CASE
 BEGIN_CASE
 mpi_mod_mpi:radix_X:input_X:radix_Y:input_Y:radix_A:input_A:div_result
 {
-    mpi X, Y, Z, A;
+    mpi X, Y, A;
     int res;
-    mpi_init( &X ); mpi_init( &Y ); mpi_init( &Z ); mpi_init( &A );
+    mpi_init( &X ); mpi_init( &Y ); mpi_init( &A );
 
     TEST_ASSERT( mpi_read_string( &X, {radix_X}, {input_X} ) == 0 );
     TEST_ASSERT( mpi_read_string( &Y, {radix_Y}, {input_Y} ) == 0 );
     TEST_ASSERT( mpi_read_string( &A, {radix_A}, {input_A} ) == 0 );
-    res = mpi_mod_mpi( &Z, &X, &Y );
+    res = mpi_mod_mpi( &X, &X, &Y );
     TEST_ASSERT( res == {div_result} );
     if( res == 0 )
     {
-        TEST_ASSERT( mpi_cmp_mpi( &Z, &A ) == 0 );
+        TEST_ASSERT( mpi_cmp_mpi( &X, &A ) == 0 );
     }
 
-    mpi_free( &X ); mpi_free( &Y ); mpi_free( &Z ); mpi_free( &A );
+    mpi_free( &X ); mpi_free( &Y ); mpi_free( &A );
 }
 END_CASE