diff --git a/src/GEval/Core.hs b/src/GEval/Core.hs
index 275a305..c269904 100644
--- a/src/GEval/Core.hs
+++ b/src/GEval/Core.hs
@@ -82,6 +82,7 @@ data GEvalException = NoExpectedFile FilePath
                       | TooFewLines
                       | TooManyLines
                       | EmptyOutput
+                      | UnexpectedData String
                       deriving (Eq)
 
 instance Exception GEvalException
@@ -97,6 +98,7 @@ instance Show GEvalException where
   show TooFewLines = "Too few lines in the output file"
   show TooManyLines = "Too many lines in the output file"
   show EmptyOutput = "The output file is empty"
+  show (UnexpectedData message) = "Unexpected data [" ++ message ++ "]"
 
 somethingWrongWithFilesMessage :: String -> FilePath -> String
 somethingWrongWithFilesMessage msg filePath = Prelude.concat
@@ -200,3 +202,4 @@ itemError (exp, out) = (exp-out)**2
 
 getValue :: Either String (Double, Text) -> Double
 getValue (Right (x, _)) = x
+getValue (Left s) = throw $ UnexpectedData s
diff --git a/test/Spec.hs b/test/Spec.hs
index 7f796fd..11f5c91 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -40,6 +40,8 @@ main = hspec $ do
       runGEvalTest "error-too-many-lines" `shouldThrow` (== TooManyLines)
     it "empty output is handled" $ do
       runGEvalTest "empty-output" `shouldThrow` (== EmptyOutput)
+    it "unexpected data is handled" $
+      runGEvalTest "unexpected-data" `shouldThrow` (== UnexpectedData "input does not start with a digit")
 
 extractVal :: (Either (ParserResult GEvalOptions) (Maybe MetricValue)) -> IO MetricValue
 extractVal (Right (Just val)) = return val
diff --git a/test/unexpected-data/unexpected-data-solution/test-A/out.tsv b/test/unexpected-data/unexpected-data-solution/test-A/out.tsv
new file mode 100644
index 0000000..ed54de3
--- /dev/null
+++ b/test/unexpected-data/unexpected-data-solution/test-A/out.tsv
@@ -0,0 +1,4 @@
+2.0
+1.1
+xyz
+2.1
diff --git a/test/unexpected-data/unexpected-data/config.txt b/test/unexpected-data/unexpected-data/config.txt
new file mode 100644
index 0000000..e2faf3d
--- /dev/null
+++ b/test/unexpected-data/unexpected-data/config.txt
@@ -0,0 +1 @@
+--metric MSE
diff --git a/test/unexpected-data/unexpected-data/test-A/expected.tsv b/test/unexpected-data/unexpected-data/test-A/expected.tsv
new file mode 100644
index 0000000..46dd6a0
--- /dev/null
+++ b/test/unexpected-data/unexpected-data/test-A/expected.tsv
@@ -0,0 +1,4 @@
+2.0
+-3.0
+1.0
+2.5
diff --git a/test/unexpected-data/unexpected-data/test-A/in.tsv b/test/unexpected-data/unexpected-data/test-A/in.tsv
new file mode 100644
index 0000000..989d482
--- /dev/null
+++ b/test/unexpected-data/unexpected-data/test-A/in.tsv
@@ -0,0 +1,4 @@
+bla 2
+bar 3
+bla 3
+bar 3