diff --git a/tests/suites/test_suite_pkcs1_v15.function b/tests/suites/test_suite_pkcs1_v15.function
index 0723623..08f590b 100644
--- a/tests/suites/test_suite_pkcs1_v15.function
+++ b/tests/suites/test_suite_pkcs1_v15.function
@@ -14,7 +14,7 @@
                               data_t * message_str, data_t * rnd_buf,
                               data_t * result_hex_str, int result )
 {
-    unsigned char output[1000];
+    unsigned char output[128];
     mbedtls_rsa_context ctx;
     rnd_buf_info info;
     mbedtls_mpi N, E;
@@ -24,7 +24,7 @@
 
     mbedtls_mpi_init( &N ); mbedtls_mpi_init( &E );
     mbedtls_rsa_init( &ctx, MBEDTLS_RSA_PKCS_V15, hash );
-    memset( output, 0x00, 1000 );
+    memset( output, 0x00, sizeof( output ) );
 
     TEST_ASSERT( mbedtls_mpi_read_string( &N, radix_N, input_N ) == 0 );
     TEST_ASSERT( mbedtls_mpi_read_string( &E, radix_E, input_E ) == 0 );
@@ -54,7 +54,7 @@
                               char * seed, data_t * message_str,
                               int result )
 {
-    unsigned char output[1000];
+    unsigned char output[128];
     mbedtls_rsa_context ctx;
     size_t output_len;
     rnd_pseudo_info rnd_info;
@@ -65,7 +65,7 @@
     mbedtls_mpi_init( &Q ); mbedtls_mpi_init( &E );
     mbedtls_rsa_init( &ctx, MBEDTLS_RSA_PKCS_V15, hash );
 
-    memset( output, 0x00, 1000 );
+    memset( output, 0x00, sizeof( output ) );
     memset( &rnd_info, 0, sizeof( rnd_pseudo_info ) );
 
     TEST_ASSERT( mbedtls_mpi_read_string( &P, radix_P, input_P ) == 0 );
@@ -248,8 +248,8 @@
                             data_t * message_str, data_t * rnd_buf,
                             data_t * result_hex_str, int result )
 {
-    unsigned char hash_result[1000];
-    unsigned char output[1000];
+    unsigned char hash_result[MBEDTLS_MD_MAX_SIZE];
+    unsigned char output[128];
     mbedtls_rsa_context ctx;
     mbedtls_mpi N, P, Q, E;
     rnd_buf_info info;
@@ -261,8 +261,8 @@
     mbedtls_mpi_init( &Q ); mbedtls_mpi_init( &E );
     mbedtls_rsa_init( &ctx, MBEDTLS_RSA_PKCS_V15, hash );
 
-    memset( hash_result, 0x00, 1000 );
-    memset( output, 0x00, 1000 );
+    memset( hash_result, 0x00, sizeof( hash_result ) );
+    memset( output, 0x00, sizeof( output ) );
 
     TEST_ASSERT( mbedtls_mpi_read_string( &P, radix_P, input_P ) == 0 );
     TEST_ASSERT( mbedtls_mpi_read_string( &Q, radix_Q, input_Q ) == 0 );
@@ -298,14 +298,14 @@
                               int hash, data_t * message_str, char * salt,
                               data_t * result_str, int result )
 {
-    unsigned char hash_result[1000];
+    unsigned char hash_result[MBEDTLS_MD_MAX_SIZE];
     mbedtls_rsa_context ctx;
     mbedtls_mpi N, E;
     ((void) salt);
 
     mbedtls_mpi_init( &N ); mbedtls_mpi_init( &E );
     mbedtls_rsa_init( &ctx, MBEDTLS_RSA_PKCS_V15, hash );
-    memset( hash_result, 0x00, 1000 );
+    memset( hash_result, 0x00, sizeof( hash_result ) );
 
     TEST_ASSERT( mbedtls_mpi_read_string( &N, radix_N, input_N ) == 0 );
     TEST_ASSERT( mbedtls_mpi_read_string( &E, radix_E, input_E ) == 0 );