diff --git a/info/Concepts/Plague.t b/info/Concepts/Plague.t
index 8cf67151..4f59333b 100644
--- a/info/Concepts/Plague.t
+++ b/info/Concepts/Plague.t
@@ -83,7 +83,7 @@ technology, population, standard of living and the Empire Plague:
 Likelihood of plague outbreak (in percent) is
         civ + mil + uw   t_level + (iron + oil + rad * 2) / 10 + 100
 max (0, -------------- * ------------------------------------------- - 1)
-              999               r_level + effic + mobil + 100
+            max_pop             r_level + effic + mobil + 100
 .FI
 .s1
 Later formulations of this relationship show great similarity
diff --git a/src/lib/update/plague.c b/src/lib/update/plague.c
index 115d9114..6e219aa0 100644
--- a/src/lib/update/plague.c
+++ b/src/lib/update/plague.c
@@ -133,7 +133,7 @@ infect_people(struct natstr *np, struct sctstr *sp)
      * make plague where there was none before...
      */
     pop = sp->sct_item[I_CIVIL] + sp->sct_item[I_MILIT] + sp->sct_item[I_UW];
-    pop_space = opt_BIG_CITY && (sp->sct_type == SCT_CAPIT) ? 9999.0 : 999.0;
+    pop_space = max_pop(np->nat_level[NAT_RLEV], sp);
     bad_stuff
 	= sp->sct_item[I_IRON] + sp->sct_item[I_OIL] + sp->sct_item[I_RAD] * 2;
     pollution = bad_stuff / 10.0 + np->nat_level[NAT_TLEV] + 100.0;