diff --git a/sources/equations.F90 b/sources/equations.F90
index ddb888e..0449be2 100644
--- a/sources/equations.F90
+++ b/sources/equations.F90
@@ -1564,7 +1564,10 @@ module equations
     integer            :: n, p, nc, np
     integer            :: i = 1, il = 1, iu = 1
     integer            :: j = 1, jl = 1, ju = 1
-    integer            :: k = 1, kl = 1, ku = 1
+    integer            :: k = 1
+#if NDIMS == 3
+    integer            :: kl = 1, ku = 1
+#endif /* NDIMS == 3 */
 
 ! temporary arrays
 !