diff --git a/core/build.sh b/core/build.sh
index 52264e3..56acb50 100755
--- a/core/build.sh
+++ b/core/build.sh
@@ -12,7 +12,7 @@ CFLAGS=(-Wall -pedantic -std=c99 -fPIC)
 LFLAGS=(-shared)
 
 echo "- translating from Python to C"
-cython -3 cython_types.pyx -o cython_types.c || die "translating"
+cython -f -3 --fast-fail -X embedsignature=True cython_types.pyx -o cython_types.c || die "translating"
 
 echo "- compiling and linking"
 gcc $CFLAGS -I/usr/include/python3.4 -pthread -c cython_types.c || die "compilation"