diff --git a/lib/resource-1.0/Makefile b/lib/resource-1.0/Makefile
index f19c428f6..ecdd4668c 100644
--- a/lib/resource-1.0/Makefile
+++ b/lib/resource-1.0/Makefile
@@ -1,7 +1,7 @@
 all: langs test
 
 test:
-	echo "gr -cat=S -number=11 -cf | tb" | gf langs.gfcm
+	echo "gr -cat=S -number=11 -prob | tb" | gf -probs=lang.gfprob langs.gfcm
 langs:
 	echo "s ;; pm | wf langs.gfcm" | gf -src */Lang??*.gf english/LangEng.gf
 
diff --git a/lib/resource-1.0/lang.gfprob b/lib/resource-1.0/lang.gfprob
new file mode 100644
index 000000000..62c68fce5
--- /dev/null
+++ b/lib/resource-1.0/lang.gfprob
@@ -0,0 +1,6 @@
+--# prob ConjNP   0.05
+--# prob ConjAP   0.1
+--# prob ConjAdv  0.1
+--# prob ConjS    0.1
+--# prob PredSCVP 0.05
+--# prob PredetNP 0.05
diff --git a/src/GF/Probabilistic/Probabilistic.hs b/src/GF/Probabilistic/Probabilistic.hs
index 9798892e4..935175ed9 100644
--- a/src/GF/Probabilistic/Probabilistic.hs
+++ b/src/GF/Probabilistic/Probabilistic.hs
@@ -200,7 +200,8 @@ hitRegion d vs = case vs of
 checkSGrammar :: SGrammar -> Err SGrammar
 checkSGrammar = mapMTree chCat where
   chCat (c,rs) = case sum [p | ((p,f),_) <- rs] of
-    s | s /= 1.0 -> Bad $ "illegal probability sum " ++ show s ++ " in " ++ c
+    s | abs (s - 1.0) > 0.01 -> 
+      Bad $ "illegal probability sum " ++ show s ++ " in " ++ c
     _ -> return (c,rs)
 
 -- for cases where explicit probability is not given (encoded as