diff --git a/src/dierckx.f90 b/src/dierckx.f90
index 8b6f5c0..4ee9771 100644
--- a/src/dierckx.f90
+++ b/src/dierckx.f90
@@ -2927,6 +2927,7 @@ contains
       ier = 0
     end if
 !  we partition the working space and determine the spline approximation
+    wrk(1) = 0
     lfpx = 5
     lfpy = lfpx+nxest
     lww = lfpy+nyest