diff --git a/src/mi/init.c b/src/mi/init.c
index 3d097717..afd97808 100644
--- a/src/mi/init.c
+++ b/src/mi/init.c
@@ -23,6 +23,7 @@ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 
+#include <assert.h>
 #include <stdlib.h>
 
 #include "internal.h"
@@ -46,7 +47,6 @@ long unwi_debug_level;
 HIDDEN void
 mi_init (void)
 {
-  extern void unw_cursor_t_is_too_small (void);
 #if UNW_DEBUG
   const char *str = getenv ("UNW_DEBUG_LEVEL");
 
@@ -60,6 +60,5 @@ mi_init (void)
     }
 #endif
 
-  if (sizeof (struct cursor) > sizeof (unw_cursor_t))
-    unw_cursor_t_is_too_small ();
+  assert (sizeof (struct cursor) <= sizeof (unw_cursor_t));
 }