diff --git a/opm/core/pressure/msmfem/partition.c b/opm/core/pressure/msmfem/partition.c
index a056258f4..a2eba6298 100644
--- a/opm/core/pressure/msmfem/partition.c
+++ b/opm/core/pressure/msmfem/partition.c
@@ -138,6 +138,7 @@ partition_compress(int n, int *p)
     int ret, i, max, *compr;
 
     max = -1;
+    assert(n > 0);
     for (i = 0; i < n; i++) {
         assert (0 <= p[i]);     /* Only non-neg partitions (for now?). */
         max = MAX(max, p[i]);
@@ -313,6 +314,9 @@ partition_create_c2c(int nc, int nneigh, const int *neigh,
 {
     int i, ret, c1, c2;
 
+    assert(nc > 0);
+    assert(nneigh > 0);
+
     *pc2c = malloc((nc + 1) * sizeof **pc2c);
 
     if (*pc2c != NULL) {