diff --git a/src/Data/Array/ST.purs b/src/Data/Array/ST.purs
index ef8b0e16..baac4e2f 100644
--- a/src/Data/Array/ST.purs
+++ b/src/Data/Array/ST.purs
@@ -100,11 +100,13 @@ foreign import pokeSTArray
   :: forall a h r
    . STArray h a -> Int -> a -> Eff (st :: ST h | r) Boolean
 
--- | Append an element to the end of a mutable array.
+-- | Append an element to the end of a mutable array. Returns the new length of
+-- | the array.
 pushSTArray :: forall a h r. STArray h a -> a -> Eff (st :: ST h | r) Int
 pushSTArray arr a = pushAllSTArray arr [a]
 
 -- | Append the values in an immutable array to the end of a mutable array.
+-- | Returns the new length of the mutable array.
 foreign import pushAllSTArray
   :: forall a h r
    . STArray h a
diff --git a/test/Test/Data/Array/ST.purs b/test/Test/Data/Array/ST.purs
index 337b59b4..78f80c73 100644
--- a/test/Test/Data/Array/ST.purs
+++ b/test/Test/Data/Array/ST.purs
@@ -42,6 +42,12 @@ testArrayST = do
     void $ pushSTArray arr 4
     pure arr) == [1, 2, 3, 4]
 
+  log "pushSTArray should return the new length of the array"
+
+  assert $ pureST (do
+    arr <- thaw [unit, unit, unit]
+    pushSTArray arr unit) == 4
+
   log "pushAllSTArray should append multiple values to the end of the array"
 
   assert $ run (do
@@ -54,6 +60,12 @@ testArrayST = do
     void $ pushAllSTArray arr [4, 5, 6]
     pure arr) == [1, 2, 3, 4, 5, 6]
 
+  log "pushAllSTArray should return the new length of the array"
+
+  assert $ pureST (do
+    arr <- thaw [unit, unit, unit]
+    pushAllSTArray arr [unit, unit]) == 5
+
   log "peekSTArray should return Nothing when peeking a value outside the array bounds"
 
   assert $ isNothing $ pureST (do