diff --git a/src/r_segs.c b/src/r_segs.c
index 1b78a22dd9d73f56a0114437077189aaca3aa1fc..1d44d9f8436d8d1788a8bc7d850abe1af569153a 100644
--- a/src/r_segs.c
+++ b/src/r_segs.c
@@ -2863,7 +2863,7 @@ static void R_DrawRepeatFlippedMaskedColumn(column_t *col)
 // R_RenderThickSegLoop
 // Like R_RenderSegLoop, but for thick sides.
 //
-void R_RenderThickSegLoop(void)
+static void R_RenderThickSegLoop(void)
 {
 	column_t *col;
 	size_t pindex;