diff --git a/tests/halcompile/command_line_flags/flags.c b/tests/halcompile/command_line_flags/flags.c
index 3b9f69461f2..391e02bdf6b 100644
--- a/tests/halcompile/command_line_flags/flags.c
+++ b/tests/halcompile/command_line_flags/flags.c
@@ -10,6 +10,7 @@
 #error This is intended as a userspace component only.
 #endif
 
+#include <stdio.h>
 #include <readline.h>
 
 int main(int argc, char **argv)