diff --git a/lib/igt_core.c b/lib/igt_core.c
index c217a016..4ae35240 100644
--- a/lib/igt_core.c
+++ b/lib/igt_core.c
@@ -209,6 +209,7 @@
  */
 
 static unsigned int exit_handler_count;
+const char *igt_interactive_debug;
 
 /* subtests helpers */
 static bool list_subtests = false;
diff --git a/lib/igt_core.h b/lib/igt_core.h
index c2c820d1..07160009 100644
--- a/lib/igt_core.h
+++ b/lib/igt_core.h
@@ -557,7 +557,7 @@ bool igt_run_in_simulation(void);
 
 void igt_skip_on_simulation(void);
 
-const char *igt_interactive_debug;
+extern const char *igt_interactive_debug;
 
 /* structured logging */
 enum igt_log_level {