diff --git a/ChangeLog b/ChangeLog
index a37282b..cfe27f3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -56,6 +56,8 @@
    * MD functions deprecated in 2.7.0 are no longer inline, to provide
      a migration path for those depending on the library's ABI.
    * Clarify the documentation of mbedtls_ssl_setup.
+   * Use (void) when defining functions with no parameters. Contributed by
+     Joris Aerts. #678
 
 = mbed TLS 2.7.0 branch released 2018-02-03
 
diff --git a/library/memory_buffer_alloc.c b/library/memory_buffer_alloc.c
index 1cfc27c..821ae2c 100644
--- a/library/memory_buffer_alloc.c
+++ b/library/memory_buffer_alloc.c
@@ -113,7 +113,7 @@
 #endif
 }
 
-static void debug_chain()
+static void debug_chain( void )
 {
     memory_header *cur = heap.first;
 
@@ -180,7 +180,7 @@
     return( 0 );
 }
 
-static int verify_chain()
+static int verify_chain( void )
 {
     memory_header *prv = heap.first, *cur;
 
@@ -504,13 +504,13 @@
     heap.verify = verify;
 }
 
-int mbedtls_memory_buffer_alloc_verify()
+int mbedtls_memory_buffer_alloc_verify( void )
 {
     return verify_chain();
 }
 
 #if defined(MBEDTLS_MEMORY_DEBUG)
-void mbedtls_memory_buffer_alloc_status()
+void mbedtls_memory_buffer_alloc_status( void )
 {
     mbedtls_fprintf( stderr,
                       "Current use: %zu blocks / %zu bytes, max: %zu blocks / "
@@ -607,7 +607,7 @@
     heap.first_free = heap.first;
 }
 
-void mbedtls_memory_buffer_alloc_free()
+void mbedtls_memory_buffer_alloc_free( void )
 {
 #if defined(MBEDTLS_THREADING_C)
     mbedtls_mutex_free( &heap.mutex );
@@ -627,7 +627,7 @@
     return( 0 );
 }
 
-static int check_all_free( )
+static int check_all_free( void )
 {
     if(
 #if defined(MBEDTLS_MEMORY_DEBUG)
diff --git a/library/version.c b/library/version.c
index 6ca80d4..fd96750 100644
--- a/library/version.c
+++ b/library/version.c
@@ -30,7 +30,7 @@
 #include "mbedtls/version.h"
 #include <string.h>
 
-unsigned int mbedtls_version_get_number()
+unsigned int mbedtls_version_get_number( void )
 {
     return( MBEDTLS_VERSION_NUMBER );
 }