diff --git a/src/mat73.c b/src/mat73.c
index b5333667..0bd898ff 100644
--- a/src/mat73.c
+++ b/src/mat73.c
@@ -3319,6 +3319,16 @@ Mat_CalcDir73(mat_t *mat, size_t *n)
     if ( NULL == mat || NULL == n )
         return MATIO_E_BAD_ARGUMENT;
 
+    if ( mat->num_datasets == 0 ) {
+        Mat_Critical("Number of datasets is zero");
+        return MATIO_E_BAD_ARGUMENT;
+    }
+
+    if ( mat->fp == NULL ) {
+        Mat_Critical("Invalid file pointer");
+        return MATIO_E_BAD_ARGUMENT;
+    }
+
     *n = 0;
     mat->dir = (char **)calloc(mat->num_datasets, sizeof(char *));
     if ( NULL == mat->dir ) {
@@ -3331,6 +3341,11 @@ Mat_CalcDir73(mat_t *mat, size_t *n)
         ssize_t name_len = H5Lget_name_by_idx(*(hid_t *)mat->fp, "/", H5_INDEX_NAME, H5_ITER_INC, i,
                                               NULL, 0, H5P_DEFAULT);
         if ( name_len < 1 ) {
+            Mat_Critical("Invalid name length returned by H5Lget_name_by_idx");
+            for ( hsize_t j = 0; j < i; j++ ) {
+                free(mat->dir[j]);
+            }
+            free(mat->dir);
             return MATIO_E_FAIL_TO_IDENTIFY;
         }
         name = (char *)malloc(name_len + 1);
@@ -3347,6 +3362,7 @@ Mat_CalcDir73(mat_t *mat, size_t *n)
             (*n)++;
         } else {
             free(name);
+            free(name);
         }
     }
     return MATIO_E_NO_ERROR;