diff --git a/chttp.c b/chttp.c
index 6d125db..dd3c8d7 100644
--- a/chttp.c
+++ b/chttp.c
@@ -3984,7 +3984,7 @@ void chttp_request_builder_target(CHTTP_RequestBuilder builder,
     conn->content_length_value_offset = byte_queue_offset(&conn->output);
 
     #define TEN_SPACES "          "
-    _Static_assert(sizeof(TEN_SPACES) == 10+1);
+    _Static_assert(sizeof(TEN_SPACES) == 10+1, "");
 
     s = CHTTP_STR(TEN_SPACES "\r\n");
     byte_queue_write(&conn->output, s.ptr, s.len);
@@ -4935,7 +4935,7 @@ static void append_special_headers(CHTTP_ServerConn *conn)
     conn->content_length_value_offset = byte_queue_offset(&conn->output);
 
     #define TEN_SPACES "          "
-    _Static_assert(sizeof(TEN_SPACES) == 10+1);
+    _Static_assert(sizeof(TEN_SPACES) == 10+1, "");
 
     s = CHTTP_STR(TEN_SPACES "\r\n");
     byte_queue_write(&conn->output, s.ptr, s.len);
diff --git a/src/client.c b/src/client.c
index a57ddda..8008f10 100644
--- a/src/client.c
+++ b/src/client.c
@@ -327,7 +327,7 @@ void chttp_request_builder_target(CHTTP_RequestBuilder builder,
     conn->content_length_value_offset = byte_queue_offset(&conn->output);
 
     #define TEN_SPACES "          "
-    _Static_assert(sizeof(TEN_SPACES) == 10+1);
+    _Static_assert(sizeof(TEN_SPACES) == 10+1, "");
 
     s = CHTTP_STR(TEN_SPACES "\r\n");
     byte_queue_write(&conn->output, s.ptr, s.len);
diff --git a/src/server.c b/src/server.c
index 5f0057a..801736e 100644
--- a/src/server.c
+++ b/src/server.c
@@ -467,7 +467,7 @@ static void append_special_headers(CHTTP_ServerConn *conn)
     conn->content_length_value_offset = byte_queue_offset(&conn->output);
 
     #define TEN_SPACES "          "
-    _Static_assert(sizeof(TEN_SPACES) == 10+1);
+    _Static_assert(sizeof(TEN_SPACES) == 10+1, "");
 
     s = CHTTP_STR(TEN_SPACES "\r\n");
     byte_queue_write(&conn->output, s.ptr, s.len);