diff --git a/library/bignum_mod.c b/library/bignum_mod.c
index 1b3aff6a3a..4303efefa6 100644
--- a/library/bignum_mod.c
+++ b/library/bignum_mod.c
@@ -39,7 +39,7 @@ int mbedtls_mpi_mod_residue_setup( mbedtls_mpi_mod_residue *r,
                                    mbedtls_mpi_uint *p,
                                    size_t p_limbs )
 {
-    if( p_limbs < m->limbs || !mbedtls_mpi_core_lt_ct( p, m->p, m->limbs ) )
+    if( p_limbs != m->limbs || !mbedtls_mpi_core_lt_ct( p, m->p, m->limbs ) )
         return( MBEDTLS_ERR_MPI_BAD_INPUT_DATA );
 
     r->limbs = m->limbs;
diff --git a/tests/suites/test_suite_bignum_mod.data b/tests/suites/test_suite_bignum_mod.data
index 02bc9f7931..ba7d5779ff 100644
--- a/tests/suites/test_suite_bignum_mod.data
+++ b/tests/suites/test_suite_bignum_mod.data
@@ -56,17 +56,17 @@ mpi_residue_setup:"fe":"01":0
 Test mbedtls_mpi_residue_setup #2 r == m - 1
 mpi_residue_setup:"ff":"fe":0
 
-Test mbedtls_mpi_residue_setup #3 m->limbs > r-> limbs && m > r
-mpi_residue_setup:"000000000000000000000000000000007dfe5c6beb35a2d6":"fe":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
+Test mbedtls_mpi_residue_setup #3 m->limbs = r-> limbs && m > r
+mpi_residue_setup:"7dfe5c6":"fe":0
 
 Test mbedtls_mpi_residue_setup #4 m->limbs = r-> limbs && m > r
 mpi_residue_setup:"7ffffffffffffffffffffffffffffffffffffffffffffff1":"0000000000000000000000000000000000000000000000fe":0
 
-Test mbedtls_mpi_residue_setup #5 m->limbs < r-> limbs && m > r
-mpi_residue_setup:"7ffffffff0000000":"000000000000000fe":0
+Test mbedtls_mpi_residue_setup #5 m->limbs > r-> limbs && m > r
+mpi_residue_setup:"7ffffffff00000000":"fe":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_residue_setup #6 m->limbs < r-> limbs && m > r
-mpi_residue_setup:"ff":"000000000000000000000000000000000000000000000001":0
+mpi_residue_setup:"ff":"000000000000000000000000000000000000000000000001":MBEDTLS_ERR_MPI_BAD_INPUT_DATA
 
 Test mbedtls_mpi_residue_setup #7 r == m
 mpi_residue_setup:"fe":"fe":-4