diff -ruN a/config/nim.cfg b/config/nim.cfg
--- a/config/nim.cfg	2018-02-15 00:45:38.251038499 +0100
+++ b/config/nim.cfg	2018-02-15 00:46:48.937858896 +0100
@@ -291,6 +291,10 @@ vcc.cpp.options.size = "/O1"
 # Configuration for the Tiny C Compiler:
 tcc.options.always = "-w"

+# Enable libucontext
+gcc.options.linker %= "-lucontext"
+llvm_gcc.options.linker %= "-lucontext"
+
 @if arm or arm64:
   --define:nimEmulateOverflowChecks
 @end