diff --git a/src/process_pipeline.c b/src/process_pipeline.c
index ddab3f4..d4dadb8 100644
--- a/src/process_pipeline.c
+++ b/src/process_pipeline.c
@@ -799,23 +799,23 @@ format_timestamp(char *timestamp)
 }
 
 static void
-format_movie_name(char *capture_fname)
+format_movie_name(size_t size, char *capture_fname)
 {
 	char timestamp[30];
 	format_timestamp(timestamp);
 
 	if (g_get_user_special_dir(G_USER_DIRECTORY_VIDEOS) != NULL) {
-		sprintf(capture_fname,
+		snprintf(capture_fname, size,
 			"%s/VID%s.mkv",
 			g_get_user_special_dir(G_USER_DIRECTORY_VIDEOS),
 			timestamp);
 	} else if (getenv("XDG_VIDOES_DIR") != NULL) {
-		sprintf(capture_fname,
+		snprintf(capture_fname, size,
 			"%s/VID%s.mkv",
 			getenv("XDG_VIDEOS_DIR"),
 			timestamp);
 	} else {
-		sprintf(capture_fname,
+		snprintf(capture_fname, size,
 			"%s/Videos/VID%s.mkv",
 			getenv("HOME"),
 			timestamp);
@@ -917,7 +917,7 @@ spawn_movie(char *cmd)
 void
 on_movie_start(void)
 {
-	format_movie_name(movie_fname);
+	format_movie_name(sizeof(movie_fname), movie_fname);
 
 	movie_recording = 1;
 	printf("movie recording on\n");