diff --git a/openGJK.c b/openGJK.c
index c7bc73e..73cb2a8 100644
--- a/openGJK.c
+++ b/openGJK.c
@@ -867,7 +867,7 @@ mexFunction(int nlhs, mxArray* plhs[], int nrhs, const mxArray* prhs[]) {
 /**
  * @brief Invoke this function from C# applications
  */
-gkFloat
+extern gkFloat
 csFunction(int nCoordsA, gkFloat* inCoordsA, int nCoordsB, gkFloat* inCoordsB) {
   gkFloat distance = 0;
   int i, j;