diff --git a/src/tinyvec.rs b/src/tinyvec.rs
index 9edf4f7..0bb84e9 100644
--- a/src/tinyvec.rs
+++ b/src/tinyvec.rs
@@ -170,11 +170,15 @@ impl<A: Array> TinyVec<A> {
 
   /// The capacity of the `TinyVec`.
   /// 
-  /// This is fixed based on the array type.
+  /// When not heap allocated this is fixed based on the array type.
+  /// Otherwise its the result of the underlying Vec::capacity.
   #[inline(always)]
   #[must_use]
   pub fn capacity(&self) -> usize {
-    A::CAPACITY
+    match self {
+      TinyVec::Inline(_) => A::CAPACITY,
+      TinyVec::Heap(v) => v.capacity(),
+    }
   }
 
   /// Removes all elements from the vec.
diff --git a/tests/tinyvec.rs b/tests/tinyvec.rs
index f539cd2..7a642ee 100644
--- a/tests/tinyvec.rs
+++ b/tests/tinyvec.rs
@@ -21,6 +21,15 @@ fn TinyVec_swap_remove() {
   assert_eq!(&tv[..], &[][..]);
 }
 
+#[test]
+fn TinyVec_capacity() {
+  let mut tv: TinyVec<[i32; 1]> = Default::default();
+  assert_eq!(tv.capacity(), 1);
+  tv.move_to_the_heap();
+  tv.extend_from_slice(&[1, 2, 3, 4]);
+  assert_eq!(tv.capacity(), 4);
+}
+
 #[test]
 fn TinyVec_drain() {
   let mut tv: TinyVec<[i32; 10]> = Default::default();