diff --git a/src/compiler/GF/Compile/GrammarToLPGF.hs b/src/compiler/GF/Compile/GrammarToLPGF.hs
index a00a75eec..7b98f32e5 100644
--- a/src/compiler/GF/Compile/GrammarToLPGF.hs
+++ b/src/compiler/GF/Compile/GrammarToLPGF.hs
@@ -131,12 +131,13 @@ mkConcrete debug (C.Abstract _ _ _ funs) (C.Concrete modId absModId flags params
       where
         val2lin :: C.LinValue -> CodeGen (L.LinFun, Maybe C.LinType)
         val2lin lv@(C.TableValue _ _) = do
+        -- val2lin lv@(C.ParamConstant _) = do
           m <- CMS.get
           case Map.lookup lv m of
             Just r -> return r
             Nothing -> do
               r <- val2lin' lv
-              CMS.put (Map.insert lv r m)
+              CMS.modify (Map.insert lv r)
               return r
         val2lin lv = val2lin' lv
 
diff --git a/testsuite/lpgf/README.md b/testsuite/lpgf/README.md
index b2738d51f..8a8300c2a 100644
--- a/testsuite/lpgf/README.md
+++ b/testsuite/lpgf/README.md
@@ -196,6 +196,15 @@ Max memory: 2.25 GB
 | PhrasebookFin | 135268 |    333 |  0.2% |
 | PhrasebookFre | 337102 |     76 | 0.02% |
 
+_modify instead of insert_
+
+| Concr         |  Total | Misses |  Perc |
+|:--------------|-------:|-------:|------:|
+| PhrasebookEng |   3211 |     70 |    2% |
+| PhrasebookSwe |   7526 |     61 |    1% |
+| PhrasebookFin | 135268 |    302 |  0.2% |
+| PhrasebookFre | 337102 |     72 | 0.02% |
+
 **Tables**
 
 | Concr         | Total | Misses | Perc |
@@ -205,9 +214,18 @@ Max memory: 2.25 GB
 | PhrasebookFin | 36875 |  21730 |  59% |
 | PhrasebookFre | 41397 |  32967 |  80% |
 
+_modify instead of insert_
+
+| Concr         | Total | Misses | Perc |
+|:--------------|------:|-------:|-----:|
+| PhrasebookEng |  2415 |   1646 |  68% |
+| PhrasebookSwe |  3228 |   2188 |  68% |
+| PhrasebookFin |  8793 |   4556 |  52% |
+| PhrasebookFre | 12490 |   5793 |  46% |
+
 Conclusions:
 - map itself requires more memory than acual compilation
-- lookup is also as also as actual compilation
+- lookup is also as slow as actual compilation
 
 Tried HashMap (deriving Hashable for LinValue), no inprovement.
 Using show on LinValue for keys is incredibly slow.