2 files changed, 3 insertions, 1 deletions

diff --git a/packages/base/src/Internal/Matrix.hs b/packages/base/src/Internal/Matrix.hs
index a7fcb47..792fe35 100644
--- a/packages/base/src/Internal/Matrix.hs
+++ b/packages/base/src/Internal/Matrix.hs
@@ -365,6 +365,7 @@ subMatrix :: Element a
             -> Matrix a -- ^ input matrix
             -> Matrix a -- ^ result
 subMatrix (r0,c0) (rt,ct) m
+    | rt <= 0 || ct <= 0 = matrixFromVector RowMajor (max 0 rt) (max 0 ct) (fromList [])
     | 0 <= r0 && 0 <= rt && r0+rt <= rows m &&
       0 <= c0 && 0 <= ct && c0+ct <= cols m = res
     | otherwise = error $ "wrong subMatrix "++show ((r0,c0),(rt,ct))++" of "++shSize m
diff --git a/packages/base/src/Internal/Modular.hs b/packages/base/src/Internal/Modular.hs
index 1d8f761..64ed2bb 100644
--- a/packages/base/src/Internal/Modular.hs
+++ b/packages/base/src/Internal/Modular.hs
@@ -442,7 +442,7 @@ test = (ok, info)
       , (checkGen (gen 5 :: Matrix R)) < 1E-15
       , (checkGen (gen 5 :: Matrix Float)) < 2E-7
       , (checkGen (cgen 5 :: Matrix C)) < 1E-15
-      , (checkGen (sgen 5 :: Matrix (Complex Float))) < 2E-7
+      , (checkGen (sgen 5 :: Matrix (Complex Float))) < 3E-7
       , (checkGen (gen 5 :: Matrix (Mod 7 I))) == 0
       , (checkGen (gen 5 :: Matrix (Mod 7 Z))) == 0
       , (checkLU (magnit 1E-10) (gen 5 :: Matrix R)) < 2E-15
@@ -461,6 +461,7 @@ test = (ok, info)
       , gm <> gm == konst 0 (3,3)
       , lgm <> lgm == konst 0 (3,3)
       , invershur tmm == luSolve' (luPacked' tmm) (ident (rows tmm))
+      , luSolve' (luPacked' (tr $ ident 5 :: Matrix (I ./. 2))) (ident 5) == ident 5
       ]