diff --git a/glm/gtc/quaternion.inl b/glm/gtc/quaternion.inl
index d1e76026..fc0fbe2d 100644
--- a/glm/gtc/quaternion.inl
+++ b/glm/gtc/quaternion.inl
@@ -480,6 +480,10 @@ namespace detail
 		T const & a
 	)
 	{
+		// Lerp is only defined in [0, 1]
+		assert(a >= T(0));
+		assert(a <= T(1));
+
 		return x * (T(1) - a) + (y * a);
 	}