diff --git a/components/newlib/platform_include/stdio.h b/components/newlib/platform_include/stdio.h
index b49167fe5f..282bc2319c 100644
--- a/components/newlib/platform_include/stdio.h
+++ b/components/newlib/platform_include/stdio.h
@@ -10,5 +10,7 @@
 #include_next <stdio.h>
 
 #if CONFIG_LIBC_PICOLIBC
+void flockfile(FILE *);
+void funlockfile(FILE *);
 FILE *open_memstream(char **, size_t *);
 #endif
diff --git a/components/newlib/test_apps/newlib/main/CMakeLists.txt b/components/newlib/test_apps/newlib/main/CMakeLists.txt
index 65505baadf..e4d322f76d 100644
--- a/components/newlib/test_apps/newlib/main/CMakeLists.txt
+++ b/components/newlib/test_apps/newlib/main/CMakeLists.txt
@@ -5,6 +5,7 @@ set(srcs
     "test_misc.c"
     "test_memstream.c"
     "test_newlib.c"
+    "test_printf.c"
     "test_setjmp.c"
     "test_stdatomic.c"
     "test_time.c")