diff --git a/library/aead_chacha20_poly1305.c b/library/aead_chacha20_poly1305.c
index 2e07f1ed4..f00380c0b 100644
--- a/library/aead_chacha20_poly1305.c
+++ b/library/aead_chacha20_poly1305.c
@@ -421,7 +421,7 @@ static const unsigned char test_mac[1][16] =
 
 int mbedtls_aead_chacha20_poly1305_self_test( int verbose )
 {
-    size_t i;
+    unsigned i;
     int result;
     unsigned char output[200];
     unsigned char mac[16];
@@ -430,7 +430,7 @@ int mbedtls_aead_chacha20_poly1305_self_test( int verbose )
     {
         if ( verbose != 0 )
         {
-            mbedtls_printf( "  ChaCha20-Poly1305 test %zu ", i );
+            mbedtls_printf( "  ChaCha20-Poly1305 test %u ", i );
         }
 
         result = mbedtls_aead_chacha20_poly1305_crypt_and_mac( test_key[i],
diff --git a/library/chacha20.c b/library/chacha20.c
index 5d2c3e5bf..28133a675 100644
--- a/library/chacha20.c
+++ b/library/chacha20.c
@@ -554,14 +554,14 @@ static const size_t test_lengths[2] =
 int mbedtls_chacha20_self_test( int verbose )
 {
     unsigned char output[381];
-    size_t i;
+    unsigned i;
     int result;
 
     for ( i = 0U; i < 2U; i++ )
     {
         if ( verbose != 0 )
         {
-            mbedtls_printf( "  ChaCha20 test %zu ", i );
+            mbedtls_printf( "  ChaCha20 test %u ", i );
         }
 
         result = mbedtls_chacha20_crypt( test_keys[i],
diff --git a/library/poly1305.c b/library/poly1305.c
index 6acbc7fa5..5a096586d 100644
--- a/library/poly1305.c
+++ b/library/poly1305.c
@@ -485,14 +485,14 @@ static const unsigned char test_mac[2][16] =
 int mbedtls_poly1305_self_test( int verbose )
 {
     unsigned char mac[16];
-    size_t i;
+    unsigned i;
     int result;
 
     for ( i = 0U; i < 2U; i++ )
     {
         if ( verbose != 0 )
         {
-            mbedtls_printf( "  Poly1305 test %zu ", i );
+            mbedtls_printf( "  Poly1305 test %u ", i );
         }
 
         result = mbedtls_poly1305_mac( test_keys[i],