diff --git a/z_spm.c b/z_spm.c
index 7cc4fd861efa2850e7156c5b549d8455751b1e63..cf1806a4ce04ac4376ba5097a3345b97a9955a62 100644
--- a/z_spm.c
+++ b/z_spm.c
@@ -158,8 +158,8 @@ z_spmMergeDuplicate( pastix_spm_t *spm )
 
             colptr[1] = idx + baseval;
         }
-        assert( ((merge == 0) && (spm->nnz         == idx+baseval)) ||
-                ((merge != 0) && (spm->nnz - merge == idx+baseval)) );
+        assert( ((merge == 0) && (spm->nnz         == idx)) ||
+                ((merge != 0) && (spm->nnz - merge == idx)) );
 
         if (merge > 0) {
             spm->nnz = spm->nnz - merge;