diff --git a/Tupfile.lua b/Tupfile.lua
index b2d504d1..ae0b23d4 100644
--- a/Tupfile.lua
+++ b/Tupfile.lua
@@ -65,8 +65,8 @@ rule(
 
 local input = {}
 for file in iter(glob{"newsrc/models/*"}) do
-    local base = tup.base(file)
-    if base:find("-b") or base:find("-s") then
+    local sd = spritedata(tup.base(file))
+    if sd.data.b or sd.data.s then
         goto continue
     end
     input += file
@@ -130,7 +130,8 @@ end
 local dexMissing = {}
 for file in iter(glob{"newsrc/sprites/gen5/*.gif", "newsrc/models/*.gif"}) do
     local base = tup.base(file)
-    if base:find("-b") or base:find("-s") or dexSet[base] then
+    local sd = spritedata(base)
+    if sd.data.b or sd.data.s or dexSet[base] then
         goto continue
     end
     dexMissing += file
diff --git a/Tuprules.lua b/Tuprules.lua
index 62e97f20..5e8a454c 100644
--- a/Tuprules.lua
+++ b/Tuprules.lua
@@ -2,6 +2,7 @@
 tup.include("util/strict.lua")
 tup.include("util/lua-ext.lua")
 tup.include("util/tup-ext.lua")
+tup.include("util/sprites.lua")
 
 ROOTDIR = tup.getcwd()
 
diff --git a/util/sprites.lua b/util/sprites.lua
new file mode 100644
index 00000000..d18b6d45
--- /dev/null
+++ b/util/sprites.lua
@@ -0,0 +1,15 @@
+
+function spritedata(basename)
+    local iter = basename:gmatch("[^-]+")
+    local result = {id = iter(), data = {}}
+    for flagtext in iter do
+        if flagtext:len() == 1 then
+            result.data[flagtext] = true
+        else
+            local flag = flagtext.sub(1, 1)
+            local text = flagtext.sub(2)
+            result.data[flag] = text
+        end
+    end
+    return result
+end