diff --git a/src/Data/Store/Core.hs b/src/Data/Store/Core.hs
--- a/src/Data/Store/Core.hs
+++ b/src/Data/Store/Core.hs
@@ -231,6 +231,18 @@
         show needed ++ ", but only " ++
         show remaining ++ " remain."
 
+-- | Throws a 'PeekException' about an attempt to read a negative number of bytes.
+--
+-- This can happen when we read invalid data -- the length tag is
+-- basically random in this case.
+negativeBytes :: Int -> Int -> String -> IO void
+negativeBytes needed remaining ty =
+    throwIO $ PeekException remaining $ T.pack $
+        "Attempted to read negative number of bytes for " ++
+        ty ++
+        ". Tried to read " ++
+        show needed ++ ".  This probably means that we're trying to read invalid data."
+
 ------------------------------------------------------------------------
 -- Decoding and encoding ByteStrings
 
@@ -382,6 +394,8 @@
             remaining = end `minusPtr` sourcePtr
         when (len > remaining) $ -- Do not perform the check on the new pointer, since it could have overflowed
             tooManyBytes len remaining ty
+        when (len < 0) $
+            negativeBytes len remaining ty
         fp <- BS.mallocByteString len
         withForeignPtr fp $ \targetPtr ->
             BS.memcpy targetPtr (castPtr sourcePtr) len
@@ -424,6 +438,8 @@
             remaining = end `minusPtr` sourcePtr
         when (len > remaining) $ -- Do not perform the check on the new pointer, since it could have overflowed
             tooManyBytes len remaining ty
+        when (len < 0) $
+            negativeBytes len remaining ty
         marr <- newByteArray len
         copyAddrToByteArray sourcePtr marr 0 len
         x <- unsafeFreezeByteArray marr
diff --git a/store-core.cabal b/store-core.cabal
--- a/store-core.cabal
+++ b/store-core.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           store-core
-version:        0.2.0.1
+version:        0.2.0.2
 synopsis:       Fast and lightweight binary serialization
 category:       Serialization, Data
 homepage:       https://github.com/fpco/store#readme