diff --git a/src/internal.h b/src/internal.h
index 4cd5bf6..09970e0 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -26,7 +26,7 @@
 #else
 #define assert_message(check, message) do {				\
     if (!(check))							\
-      errx(1, "Assertation failed (programmer error): %s", message);	\
+      errx(1, "Assertion failed (programmer error): %s", message);	\
   } while(0)
 #endif
 #define false 0