diff --git a/crystal.cpp b/crystal.cpp
index 15e4e5a6..f601e3e3 100644
--- a/crystal.cpp
+++ b/crystal.cpp
@@ -305,8 +305,6 @@ ld sqhypot2(crystal_structure& cs, ldcoord co1, ldcoord co2) {
   return result;
   }
 
-void crystalstep(heptagon *h, int d);
-
 static const int Modval = 64;
 
 struct east_structure {