2 files changed, 6 insertions, 0 deletions
diff --git a/src/deco.c b/src/deco.c
index 80853b8..29f07ea 100644
--- a/src/deco.c
+++ b/src/deco.c
@@ -293,6 +293,8 @@ void init_tissues(decostate_t *ds)
 
 void init_decostate(decostate_t *ds, const unsigned char gflo, const unsigned char gfhi, const double ceil_multiple)
 {
+    assert(gflo <= gfhi);
+
     init_tissues(ds);
 
     ds->gflo = gflo;
diff --git a/src/opendeco.c b/src/opendeco.c
index ae95f58..5051633 100644
--- a/src/opendeco.c
+++ b/src/opendeco.c
@@ -98,6 +98,10 @@ static error_t parse_opt(int key, char *arg, struct argp_state *state)
             argp_failure(state, 1, 0, "Surface air pressure must be positive. See --help for more information");
             exit(ARGP_ERR_UNKNOWN);
         }
+        if (arguments->gflow > arguments->gfhigh) {
+            argp_failure(state, 1, 0, "GF Low must not be greater than GF High");
+            exit(ARGP_ERR_UNKNOWN);
+        }
     default:
         return ARGP_ERR_UNKNOWN;
     }