diff -up src/sage/modular/arithgroup/farey.cpp.orig src/sage/modular/arithgroup/farey.cpp
--- src/sage/modular/arithgroup/farey.cpp.orig	2016-08-08 13:04:25.463462742 -0400
+++ src/sage/modular/arithgroup/farey.cpp	2016-08-08 13:04:47.129463572 -0400
@@ -142,6 +142,7 @@ operator*(const SL2Z& M, const vector<mp
   return result;
 }
 
+#if 0
 inline 
 mpz_class 
 floor(const mpq_class r) {
@@ -152,6 +153,7 @@ floor(const mpq_class r) {
     return result - 1;
   }
 }
+#endif
 
 inline
 mpz_class lcm(const mpz_class& a, const mpz_class& b) {