diff --git a/src/runtime/common/bytes.h b/src/runtime/common/bytes.h
index 66d1bae..de28f56 100644
--- a/src/runtime/common/bytes.h
+++ b/src/runtime/common/bytes.h
@@ -20,6 +20,6 @@
 
 value alloc_bytes( asize_t size );
 value bytes_of_string( value s );
-struct custom_operations bytes_ops;
+extern struct custom_operations bytes_ops;
 
 #endif /* _bytes_ */
diff --git a/src/runtime/core/failexn.h b/src/runtime/core/failexn.h
index eac1e89..c45234a 100644
--- a/src/runtime/core/failexn.h
+++ b/src/runtime/core/failexn.h
@@ -78,7 +78,7 @@ struct exception_frame {
                    } \
                  }
 
-struct exception_frame* global_exn_frame;
+extern struct exception_frame* global_exn_frame;
 
 
 #endif /* _failexn_h */