diff --git a/copilot-language/src/Copilot/Language/Analyze.hs b/copilot-language/src/Copilot/Language/Analyze.hs
index e7065f7b4..1b72c9aed 100644
--- a/copilot-language/src/Copilot/Language/Analyze.hs
+++ b/copilot-language/src/Copilot/Language/Analyze.hs
@@ -188,7 +188,7 @@ analyzeAppend refStreams dstn e b f = do
 -- append.
 analyzeDrop :: Int -> Stream a -> IO ()
 analyzeDrop k (Append xs _ _)
-  | k >= length xs                         = throw DropIndexOverflow
+  | k > length xs                          = throw DropIndexOverflow
   | k > fromIntegral (maxBound :: DropIdx) = throw DropMaxViolation
   | otherwise                              = return ()
 analyzeDrop _ _                            = throw DropAppliedToNonAppend
diff --git a/copilot-language/src/Copilot/Language/Operators/Temporal.hs b/copilot-language/src/Copilot/Language/Operators/Temporal.hs
index 37b0d9a22..45ce5c119 100644
--- a/copilot-language/src/Copilot/Language/Operators/Temporal.hs
+++ b/copilot-language/src/Copilot/Language/Operators/Temporal.hs
@@ -1,5 +1,4 @@
 -- Copyright © 2011 National Institute of Aerospace / Galois, Inc.
-
 {-# LANGUAGE Safe #-}
 
 -- | Temporal stream transformations.
@@ -11,7 +10,7 @@ module Copilot.Language.Operators.Temporal
 import Copilot.Core (Typed)
 import Copilot.Language.Prelude
 import Copilot.Language.Stream
-import Prelude ()
+import Prelude ((==))
 
 infixr 1 ++
 
@@ -32,8 +31,11 @@ infixr 1 ++
 -- elements. For most kinds of streams, you cannot drop elements without
 -- prepending an equal or greater number of elements to them first, as it
 -- could result in undefined samples.
-drop :: Typed a => Int -> Stream a -> Stream a
-drop 0 s             = s
-drop _ ( Const j )   = Const j
-drop i ( Drop  j s ) = Drop (fromIntegral i + j) s
-drop i s             = Drop (fromIntegral i)     s
+drop :: (Typed a) => Int -> Stream a -> Stream a
+drop 0 s                                = s
+-- Along with simplifying the Stream, this also avoids the invalid C code
+-- generated from append (array) and drop (indexing) when their lengths are the same
+drop i ( Append a _ s ) | i == length a = s
+drop _ ( Const j )                      = Const j
+drop i ( Drop  j s )                    = Drop (fromIntegral i + j) s
+drop i s                                = Drop (fromIntegral i)     s