diff --git a/ChangeLog b/ChangeLog
index 27a6eab78..f0a015707 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,7 @@ Changes
    * Split off curves from ecp.c into ecp_curves.c
 
 Bugfix
+   * Fixed bug in mpi_set_bit() on platforms where t_uint is wider than int
    * Fixed X.509 hostname comparison (with non-regular characters)
    * SSL now gracefully handles missing RNG
    * Missing defines / cases for RSA_PSK key exchange
diff --git a/library/bignum.c b/library/bignum.c
index 945da17b8..98d534a5a 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -280,7 +280,8 @@ int mpi_set_bit( mpi *X, size_t pos, unsigned char val )
         MPI_CHK( mpi_grow( X, off + 1 ) );
     }
 
-    X->p[off] = ( X->p[off] & ~( 0x01 << idx ) ) | ( val << idx );
+    X->p[off] &= ~( (t_uint) 0x01 << idx );
+    X->p[off] |= (t_uint) val << idx;
 
 cleanup:
     
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index b9e00f1d7..36ae8d6a8 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -665,6 +665,12 @@ mpi_set_bit:10:"49979687":80:0:10:"49979687"
 Test bit set (Add above existing limbs with a 1)
 mpi_set_bit:10:"49979687":80:1:10:"1208925819614629224685863"
 
+Test bit set (Bit index larger than 31 with a 0)
+mpi_set_bit:16:"FFFFFFFFFFFFFFFF":32:0:16:"FFFFFFFEFFFFFFFF"
+
+Test bit set (Bit index larger than 31 with a 1)
+mpi_set_bit:16:"00":32:1:16:"0100000000"
+
 MPI Selftest
 depends_on:POLARSSL_SELF_TEST
 mpi_selftest: