diff --git a/src/input.rs b/src/input.rs
index a0fa03e..e784398 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -152,10 +152,8 @@ impl<'ui, 'p> InputText<'ui, 'p> {
     pub fn build(self) -> bool {
         unsafe {
             imgui_sys::igInputText(self.label.as_ptr(),
-                                   // TODO: this is evil.
-                                   // Perhaps something else than &mut str is better
                                    self.buf.as_ptr() as *mut i8,
-                                   self.buf.capacity() + 1,
+                                   self.buf.capacity_with_nul(),
                                    self.flags,
                                    None,
                                    ptr::null_mut())
diff --git a/src/string.rs b/src/string.rs
index 1af1c5b..8cc1dd0 100644
--- a/src/string.rs
+++ b/src/string.rs
@@ -35,6 +35,7 @@ impl ImString {
         self.0.push(b'\0');
     }
     pub fn capacity(&self) -> usize { self.0.capacity() - 1 }
+    pub fn capacity_with_nul(&self) -> usize { self.0.capacity() }
     pub fn reserve(&mut self, additional: usize) {
         self.0.reserve(additional);
     }