diff --git a/src/libnm-glib-aux/nm-shared-utils.c b/src/libnm-glib-aux/nm-shared-utils.c
index 22354d17df..b41e517ee1 100644
--- a/src/libnm-glib-aux/nm-shared-utils.c
+++ b/src/libnm-glib-aux/nm-shared-utils.c
@@ -761,7 +761,7 @@ out:
 
 /*****************************************************************************/
 
-char _nm_utils_to_string_buffer[];
+_nm_thread_local char _nm_utils_to_string_buffer[] = {0};
 
 void
 nm_utils_to_string_buffer_init(char **buf, gsize *len)
diff --git a/src/libnm-glib-aux/nm-shared-utils.h b/src/libnm-glib-aux/nm-shared-utils.h
index 975897602d..16aa6904de 100644
--- a/src/libnm-glib-aux/nm-shared-utils.h
+++ b/src/libnm-glib-aux/nm-shared-utils.h
@@ -1048,7 +1048,7 @@ int _nm_utils_ascii_str_to_bool(const char *str, int default_value);
 
 /*****************************************************************************/
 
-extern char _nm_utils_to_string_buffer[2096];
+_nm_thread_local extern char _nm_utils_to_string_buffer[2096];
 
 void     nm_utils_to_string_buffer_init(char **buf, gsize *len);
 gboolean nm_utils_to_string_buffer_init_null(gconstpointer obj, char **buf, gsize *len);