diff --git a/bindings/f95/strutil.f90 b/bindings/f95/strutil.f90
index 9a69ffd..69dd3ce 100644
--- a/bindings/f95/strutil.f90
+++ b/bindings/f95/strutil.f90
@@ -59,7 +59,7 @@
       end subroutine plstrc2f
 
 
-      integer function islen(string)
+      integer*4 function islen(string)
       character*(*) string
       integer i