diff --git a/library/bignum.c b/library/bignum.c
index 20afa22d5d..75c7439f46 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1587,17 +1587,17 @@ cleanup:
  */
 int mbedtls_mpi_add_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint b )
 {
-    mbedtls_mpi _B;
+    mbedtls_mpi B;
     mbedtls_mpi_uint p[1];
     MPI_VALIDATE_RET( X != NULL );
     MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
-    _B.s = ( b < 0 ) ? -1 : 1;
-    _B.n = 1;
-    _B.p = p;
+    B.s = ( b < 0 ) ? -1 : 1;
+    B.n = 1;
+    B.p = p;
 
-    return( mbedtls_mpi_add_mpi( X, A, &_B ) );
+    return( mbedtls_mpi_add_mpi( X, A, &B ) );
 }
 
 /*
@@ -1605,17 +1605,17 @@ int mbedtls_mpi_add_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
  */
 int mbedtls_mpi_sub_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint b )
 {
-    mbedtls_mpi _B;
+    mbedtls_mpi B;
     mbedtls_mpi_uint p[1];
     MPI_VALIDATE_RET( X != NULL );
     MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
-    _B.s = ( b < 0 ) ? -1 : 1;
-    _B.n = 1;
-    _B.p = p;
+    B.s = ( b < 0 ) ? -1 : 1;
+    B.n = 1;
+    B.p = p;
 
-    return( mbedtls_mpi_sub_mpi( X, A, &_B ) );
+    return( mbedtls_mpi_sub_mpi( X, A, &B ) );
 }
 
 /** Helper for mbedtls_mpi multiplication.
@@ -2027,16 +2027,16 @@ int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R,
                          const mbedtls_mpi *A,
                          mbedtls_mpi_sint b )
 {
-    mbedtls_mpi _B;
+    mbedtls_mpi B;
     mbedtls_mpi_uint p[1];
     MPI_VALIDATE_RET( A != NULL );
 
     p[0] = ( b < 0 ) ? -b : b;
-    _B.s = ( b < 0 ) ? -1 : 1;
-    _B.n = 1;
-    _B.p = p;
+    B.s = ( b < 0 ) ? -1 : 1;
+    B.n = 1;
+    B.p = p;
 
-    return( mbedtls_mpi_div_mpi( Q, R, A, &_B ) );
+    return( mbedtls_mpi_div_mpi( Q, R, A, &B ) );
 }
 
 /*