diff --git a/libio/tst-bz24051.c b/libio/tst-bz24051.c
index a9903f20a3..2d32aae74a 100644
--- a/libio/tst-bz24051.c
+++ b/libio/tst-bz24051.c
@@ -19,7 +19,11 @@
 
 /* Prevent putchar -> _IO_putc inline expansion.  */
 #define __NO_INLINE__
-#pragma GCC optimize("O0")
+#ifdef __clang__
+# pragma clang optimize off
+#else
+# pragma GCC optimize("O0")
+#endif
 
 #include <stdio.h>
 #include <string.h>
diff --git a/libio/tst-bz24153.c b/libio/tst-bz24153.c
index 023f07ca20..c379876fcc 100644
--- a/libio/tst-bz24153.c
+++ b/libio/tst-bz24153.c
@@ -18,7 +18,11 @@
 
 /* Prevent getchar -> getc inline expansion.  */
 #define __NO_INLINE__
-#pragma GCC optimize ("O0")
+#ifdef __clang__
+# pragma clang optimize off
+#else
+# pragma GCC optimize("O0")
+#endif
 
 #include <stdarg.h>
 #include <stdio.h>