diff --git a/src/hybsys_global.c b/src/hybsys_global.c
index 8fe71c74..3a2af4a7 100644
--- a/src/hybsys_global.c
+++ b/src/hybsys_global.c
@@ -354,7 +354,8 @@ hybsys_global_assemble_cell(int nconn, int *conn,
         for (jl = 0; jl < nconn; jl++) {
             jg = csrmatrix_elm_index(ig, conn[jl], A);
 
-            assert ((A->ia[ig] <= jg) && (jg < A->ia[ig + 1]));
+            assert ((((size_t)(A->ia[ig])) <= jg) &&
+                    (jg < ((size_t)(A->ia[ig + 1]))));
 
             A->sa[jg] += S[il + jl*nconn]; /* Row major per cell */
         }
diff --git a/src/sparse_sys.c b/src/sparse_sys.c
index f018fed9..67a0755e 100644
--- a/src/sparse_sys.c
+++ b/src/sparse_sys.c
@@ -209,7 +209,7 @@ csrmatrix_write(const struct CSRMatrix *A, const char *fn)
     fp = fopen(fn, "wt");
 
     if (fp != NULL) {
-        for (i = j = 0; i < A->m; i++) {
+        for (i = j = 0; (size_t)i < A->m; i++) {
             for (; j < A->ia[i + 1]; j++) {
                 fprintf(fp, "%lu %lu %26.18e\n",
                         (unsigned long) (i + 1),