diff --git a/src/xrCore/_sphere.h b/src/xrCore/_sphere.h
index 2162e429142..d965ff2317e 100644
--- a/src/xrCore/_sphere.h
+++ b/src/xrCore/_sphere.h
@@ -1,6 +1,11 @@
 #ifndef _F_SPHERE_H_
 #define _F_SPHERE_H_
 
+template <class T> struct _sphere;
+
+typedef _sphere<float> Fsphere;
+typedef _sphere<double> Dsphere;
+
 template <class T>
 struct _sphere
 {
@@ -162,9 +167,6 @@ struct _sphere
     }
 };
 
-typedef _sphere<float> Fsphere;
-typedef _sphere<double> Dsphere;
-
 template <class T>
 BOOL _valid(const _sphere<T>& s) { return _valid(s.P) && _valid(s.R); }