diff --git a/core/fifo.c b/core/fifo.c
index 1a92d9bc..c59adb55 100644
--- a/core/fifo.c
+++ b/core/fifo.c
@@ -114,6 +114,11 @@ int uwsgi_master_fifo_manage(int fd) {
 		return 0;
 	}
 
+	if ((int)cmd < 0) {
+		uwsgi_error("invalid cmd read in uwsgi_master_fifo_manage");
+		exit(1);
+	}
+
 	if (uwsgi_fifo_table[(int) cmd]) {
 		uwsgi_fifo_table[(int) cmd](0);
 	}
diff --git a/core/utils.c b/core/utils.c
index 48071ba8..fdf431f4 100644
--- a/core/utils.c
+++ b/core/utils.c
@@ -1222,7 +1222,7 @@ void uwsgi_linux_ksm_map(void) {
 	}
 
 	// we now have areas
-	if (uwsgi.ksm_mappings_last_size == 0 || uwsgi.ksm_mappings_current_size == 0 || uwsgi.ksm_mappings_current_size != uwsgi.ksm_mappings_last_size) {
+	if (uwsgi.ksm_mappings_last_size == 0 || uwsgi.ksm_mappings_current_size != uwsgi.ksm_mappings_last_size) {
 		dirty = 1;
 	}
 	else {
diff --git a/plugins/gevent/gevent.c b/plugins/gevent/gevent.c
index 1fbe14ff..fd44bbda 100644
--- a/plugins/gevent/gevent.c
+++ b/plugins/gevent/gevent.c
@@ -291,7 +291,8 @@ request:
 	}
 
 end:
-	Py_DECREF(greenlet_switch);
+	if (greenlet_switch)
+		Py_DECREF(greenlet_switch);
 end2:
 	Py_DECREF(current_greenlet);
 
diff --git a/plugins/router_hash/router_hash.c b/plugins/router_hash/router_hash.c
index 7e980f8e..812a4992 100644
--- a/plugins/router_hash/router_hash.c
+++ b/plugins/router_hash/router_hash.c
@@ -81,7 +81,7 @@ static int uwsgi_routing_func_hash(struct wsgi_request *wsgi_req, struct uwsgi_r
 			vallen = urhc->items_len;
 		}
 		// last item
-		else {
+		else if (value != NULL) {
 			vallen = (urhc->items + urhc->items_len) - value;
 		}
 	}