diff --git a/ChangeLog.d/bugfix_3782.txt b/ChangeLog.d/bugfix_3782.txt
new file mode 100644
index 000000000..25e18cb18
--- /dev/null
+++ b/ChangeLog.d/bugfix_3782.txt
@@ -0,0 +1,2 @@
+Bugfix
+  * Fix build failures on GCC 11. Fixes #3782.
diff --git a/library/cmac.c b/library/cmac.c
index 816bf13da..59ece155e 100644
--- a/library/cmac.c
+++ b/library/cmac.c
@@ -420,7 +420,7 @@ exit:
  */
 int mbedtls_aes_cmac_prf_128( const unsigned char *key, size_t key_length,
                               const unsigned char *input, size_t in_len,
-                              unsigned char *output )
+                              unsigned char output[16] )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     const mbedtls_cipher_info_t *cipher_info;
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 041578e68..a1a5859f0 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -680,20 +680,20 @@ static void ssl_calc_finished_ssl( mbedtls_ssl_context *, unsigned char *, int )
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
-static void ssl_calc_verify_tls( const mbedtls_ssl_context *, unsigned char *, size_t * );
+static void ssl_calc_verify_tls( const mbedtls_ssl_context *, unsigned char*, size_t * );
 static void ssl_calc_finished_tls( mbedtls_ssl_context *, unsigned char *, int );
 #endif
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
 static void ssl_update_checksum_sha256( mbedtls_ssl_context *, const unsigned char *, size_t );
-static void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *,unsigned char *, size_t * );
+static void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *,unsigned char*, size_t * );
 static void ssl_calc_finished_tls_sha256( mbedtls_ssl_context *,unsigned char *, int );
 #endif
 
 #if defined(MBEDTLS_SHA512_C)
 static void ssl_update_checksum_sha384( mbedtls_ssl_context *, const unsigned char *, size_t );
-static void ssl_calc_verify_tls_sha384( const mbedtls_ssl_context *, unsigned char *, size_t * );
+static void ssl_calc_verify_tls_sha384( const mbedtls_ssl_context *, unsigned char*, size_t * );
 static void ssl_calc_finished_tls_sha384( mbedtls_ssl_context *, unsigned char *, int );
 #endif
 #endif /* MBEDTLS_SSL_PROTO_TLS1_2 */
@@ -1667,7 +1667,7 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
 
 #if defined(MBEDTLS_SSL_PROTO_SSL3)
 void ssl_calc_verify_ssl( const mbedtls_ssl_context *ssl,
-                          unsigned char hash[36],
+                          unsigned char *hash,
                           size_t *hlen )
 {
     mbedtls_md5_context md5;
@@ -1720,7 +1720,7 @@ void ssl_calc_verify_ssl( const mbedtls_ssl_context *ssl,
 
 #if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1)
 void ssl_calc_verify_tls( const mbedtls_ssl_context *ssl,
-                          unsigned char hash[36],
+                          unsigned char *hash,
                           size_t *hlen )
 {
     mbedtls_md5_context md5;
@@ -1752,7 +1752,7 @@ void ssl_calc_verify_tls( const mbedtls_ssl_context *ssl,
 #if defined(MBEDTLS_SSL_PROTO_TLS1_2)
 #if defined(MBEDTLS_SHA256_C)
 void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *ssl,
-                                 unsigned char hash[32],
+                                 unsigned char *hash,
                                  size_t *hlen )
 {
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
@@ -1801,7 +1801,7 @@ void ssl_calc_verify_tls_sha256( const mbedtls_ssl_context *ssl,
 
 #if defined(MBEDTLS_SHA512_C)
 void ssl_calc_verify_tls_sha384( const mbedtls_ssl_context *ssl,
-                                 unsigned char hash[48],
+                                 unsigned char *hash,
                                  size_t *hlen )
 {
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
@@ -3197,6 +3197,9 @@ static void ssl_calc_finished_tls_sha256(
 #endif /* MBEDTLS_SHA256_C */
 
 #if defined(MBEDTLS_SHA512_C)
+
+typedef int (*finish_sha384_t)(mbedtls_sha512_context*, unsigned char*);
+
 static void ssl_calc_finished_tls_sha384(
                 mbedtls_ssl_context *ssl, unsigned char *buf, int from )
 {
@@ -3255,8 +3258,14 @@ static void ssl_calc_finished_tls_sha384(
     MBEDTLS_SSL_DEBUG_BUF( 4, "finished sha512 state", (unsigned char *)
                    sha512.state, sizeof( sha512.state ) );
 #endif
+    /*
+     * For SHA-384, we can save 16 bytes by keeping padbuf 48 bytes long.
+     * However, to avoid stringop-overflow warning in gcc, we have to cast
+     * mbedtls_sha512_finish_ret().
+     */
+    finish_sha384_t finish = (finish_sha384_t)mbedtls_sha512_finish_ret;
+    finish( &sha512, padbuf );
 
-    mbedtls_sha512_finish_ret( &sha512, padbuf );
     mbedtls_sha512_free( &sha512 );
 #endif
 
diff --git a/programs/test/selftest.c b/programs/test/selftest.c
index 2aa379b1c..41d704073 100644
--- a/programs/test/selftest.c
+++ b/programs/test/selftest.c
@@ -158,7 +158,7 @@ static int calloc_self_test( int verbose )
 }
 #endif /* MBEDTLS_SELF_TEST */
 
-static int test_snprintf( size_t n, const char ref_buf[10], int ref_ret )
+static int test_snprintf( size_t n, const char *ref_buf, int ref_ret )
 {
     int ret;
     char buf[10] = "xxxxxxxxx";
diff --git a/tests/suites/host_test.function b/tests/suites/host_test.function
index db53e9784..872a3a43a 100644
--- a/tests/suites/host_test.function
+++ b/tests/suites/host_test.function
@@ -335,7 +335,7 @@ static int convert_params( size_t cnt , char ** params , int * int_params_store
 #if defined(__GNUC__)
 __attribute__((__noinline__))
 #endif
-static int test_snprintf( size_t n, const char ref_buf[10], int ref_ret )
+static int test_snprintf( size_t n, const char *ref_buf, int ref_ret )
 {
     int ret;
     char buf[10] = "xxxxxxxxx";