diff --git a/polymer/eduke32/build/src/polymost.c b/polymer/eduke32/build/src/polymost.c
index c7499a51f..d9aa2237d 100644
--- a/polymer/eduke32/build/src/polymost.c
+++ b/polymer/eduke32/build/src/polymost.c
@@ -5935,9 +5935,16 @@ static int32_t osdcmd_cvar_set_polymost(const osdfuncparm_t *parm)
         {
             if (pr_maxlightpasses != r_pr_maxlightpasses)
             {
+                int32_t i = 0;
 
+                while (i < PR_MAXLIGHTS)
+                {
+                    if (prlights[i].flags.active)
+                        prlights[i].flags.invalidate = 1;
+                    i++;
+                }
+                pr_maxlightpasses = r_pr_maxlightpasses;
             }
-            pr_maxlightpasses = r_pr_maxlightpasses;
             return r;
         }
 #endif