diff --git a/dat/themerms.lua b/dat/themerms.lua
index b7e0f1f0a..64c1b316e 100644
--- a/dat/themerms.lua
+++ b/dat/themerms.lua
@@ -936,7 +936,7 @@ function themerooms_generate()
       themerooms[actualrm].contents();
       return
    end
-   local pick = 1;
+   local pick = nil;
    local total_frequency = 0;
    for i = 1, #themerooms do
       if (type(themerooms[i]) ~= "table") then
@@ -957,6 +957,10 @@ function themerooms_generate()
          end
       end
    end
+   if pick == nil then
+      nh.impossible('no eligible themed rooms?')
+      return
+   end
    themerooms[pick].contents();
 end
 
@@ -995,7 +999,7 @@ function themeroom_fill(rm)
       end
       return
    end
-   local pick = 1;
+   local pick = nil;
    local total_frequency = 0;
    for i = 1, #themeroom_fills do
       if (type(themeroom_fills[i]) ~= "table") then
@@ -1016,6 +1020,10 @@ function themeroom_fill(rm)
          end
       end
    end
+   if pick == nil then
+      nh.impossible('no eligible themed room fills?')
+      return
+   end
    themeroom_fills[pick].contents(rm);
 end