diff --git a/libio/tst-freopen.c b/libio/tst-freopen.c
index 23ceb9694f..bb81eb58e7 100644
--- a/libio/tst-freopen.c
+++ b/libio/tst-freopen.c
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <libc-diag.h>
 
 #include <support/check.h>
 #include <support/temp_file.h>
@@ -41,7 +42,10 @@ static void
 do_test_basic (void)
 {
   const char * const test = "Let's test freopen.\n";
+  DIAG_PUSH_NEEDS_COMMENT_CLANG;
+  DIAG_IGNORE_NEEDS_COMMENT_CLANG (3.4, "-Wgnu-folding-constant");
   char temp[strlen (test) + 1];
+  DIAG_POP_NEEDS_COMMENT_CLANG;
 
   FILE *f = fdopen (fd, "w");
   if (f == NULL)
diff --git a/libio/tst-mmap-setvbuf.c b/libio/tst-mmap-setvbuf.c
index 1c24993caf..85543e8b33 100644
--- a/libio/tst-mmap-setvbuf.c
+++ b/libio/tst-mmap-setvbuf.c
@@ -20,13 +20,17 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <libc-diag.h>
 
 int main (void)
 {
   char name[] = "/tmp/tst-mmap-setvbuf.XXXXXX";
   char buf[4096];
   const char * const test = "Let's see if mmap stdio works with setvbuf.\n";
+  DIAG_PUSH_NEEDS_COMMENT_CLANG;
+  DIAG_IGNORE_NEEDS_COMMENT_CLANG (3.4, "-Wgnu-folding-constant");
   char temp[strlen (test) + 1];
+  DIAG_POP_NEEDS_COMMENT_CLANG;
   int fd = mkstemp (name);
   FILE *f;