diff --git a/programs/pkey/dh_client.c b/programs/pkey/dh_client.c
index 546b02e..0b340d5 100644
--- a/programs/pkey/dh_client.c
+++ b/programs/pkey/dh_client.c
@@ -127,7 +127,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );
 
diff --git a/programs/pkey/dh_server.c b/programs/pkey/dh_server.c
index 81c0c9f..8fda29f 100644
--- a/programs/pkey/dh_server.c
+++ b/programs/pkey/dh_server.c
@@ -134,7 +134,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );
 
diff --git a/programs/pkey/rsa_decrypt.c b/programs/pkey/rsa_decrypt.c
index de16de5..2a6c15f 100644
--- a/programs/pkey/rsa_decrypt.c
+++ b/programs/pkey/rsa_decrypt.c
@@ -120,7 +120,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );
 
diff --git a/programs/pkey/rsa_encrypt.c b/programs/pkey/rsa_encrypt.c
index a3f9a66..8604323 100644
--- a/programs/pkey/rsa_encrypt.c
+++ b/programs/pkey/rsa_encrypt.c
@@ -114,7 +114,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );
 
diff --git a/programs/pkey/rsa_sign.c b/programs/pkey/rsa_sign.c
index e2d39fc..895880f 100644
--- a/programs/pkey/rsa_sign.c
+++ b/programs/pkey/rsa_sign.c
@@ -100,7 +100,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );
 
diff --git a/programs/pkey/rsa_verify.c b/programs/pkey/rsa_verify.c
index 35467ee..3de84d6 100644
--- a/programs/pkey/rsa_verify.c
+++ b/programs/pkey/rsa_verify.c
@@ -91,7 +91,7 @@
         goto exit;
     }
 
-    rsa.len = ( mbedtls_mpi_msb( &rsa.N ) + 7 ) >> 3;
+    rsa.len = ( mbedtls_mpi_bitlen( &rsa.N ) + 7 ) >> 3;
 
     fclose( f );