diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 0.3.1
+
+* Added `justCheck` and `stackage check` command line.
+
 ## 0.3.0.1
 
 Pre-fetch all packages from Hackage to catch Hackage downtime early.
diff --git a/Stackage/CompleteBuild.hs b/Stackage/CompleteBuild.hs
--- a/Stackage/CompleteBuild.hs
+++ b/Stackage/CompleteBuild.hs
@@ -5,6 +5,7 @@
     ( BuildType (..)
     , BumpType (..)
     , completeBuild
+    , justCheck
     ) where
 import Data.Default.Class        (def)
 import Data.Semigroup            (Max (..), Option (..))
@@ -128,6 +129,25 @@
     , tshow lts
     , ".yaml"
     ]
+
+-- | Generate and check a new build plan, but do not execute it.
+--
+-- Since 0.3.1
+justCheck :: IO ()
+justCheck = withManager tlsManagerSettings $ \man -> do
+    putStrLn "Loading build constraints"
+    bc <- defaultBuildConstraints man
+
+    putStrLn "Creating build plan"
+    plan <- newBuildPlan bc
+
+    putStrLn $ "Writing build plan to check-plan.yaml"
+    encodeFile "check-plan.yaml" plan
+
+    putStrLn "Checking plan"
+    checkBuildPlan plan
+
+    putStrLn "Plan seems valid!"
 
 completeBuild :: BuildType -> IO ()
 completeBuild buildType = withManager tlsManagerSettings $ \man -> do
diff --git a/app/stackage.hs b/app/stackage.hs
--- a/app/stackage.hs
+++ b/app/stackage.hs
@@ -5,11 +5,12 @@
 main = do
     args <- getArgs
     case args of
-        [x] | Just y <- lookup x m -> completeBuild y
+        [x] | Just y <- lookup x m -> y
         _ -> error $ "Expected one argument, one of: " ++ unwords (map fst m)
   where
     m =
-        [ ("nightly", Nightly)
-        , ("lts-major", LTS Major)
-        , ("lts-minor", LTS Minor)
+        [ ("nightly", completeBuild Nightly)
+        , ("lts-major", completeBuild $ LTS Major)
+        , ("lts-minor", completeBuild $ LTS Minor)
+        , ("check", justCheck)
         ]
diff --git a/stackage.cabal b/stackage.cabal
--- a/stackage.cabal
+++ b/stackage.cabal
@@ -1,5 +1,5 @@
 name:                stackage
-version:             0.3.0.1
+version:             0.3.1
 synopsis:            "Stable Hackage," tools for creating a vetted set of packages from Hackage.
 description:         Please see <http://www.stackage.org/package/stackage> for a description and documentation.
 homepage:            https://github.com/fpco/stackage