diff --git a/geanylua/glspi_dlg.c b/geanylua/glspi_dlg.c
index a6a4c7a23..489fa1955 100644
--- a/geanylua/glspi_dlg.c
+++ b/geanylua/glspi_dlg.c
@@ -211,6 +211,7 @@ static gint glspi_message(lua_State* L)
 	case 2:
 		if (!lua_isstring(L, 2))	{ return FAIL_STRING_ARG(2); }
 		arg2=lua_tostring(L, 2);
+		/* Fallthrough */
 	default:
 		if (!lua_isstring(L, 1))	{ return FAIL_STRING_ARG(1); }
 		arg1=lua_tostring(L, 1);
@@ -280,6 +281,7 @@ static gint glspi_input(lua_State* L)
 				if (!lua_isstring(L, 2))	{ return FAIL_STRING_ARG(2); }
 				arg2=lua_tostring(L, 2);
 			}
+		/* Fallthrough */
 		default:
 			if (!lua_isnil(L, 1)) {
 				if (!lua_isstring(L, 1))	{ return FAIL_STRING_ARG(1); }
diff --git a/geanylua/glspi_doc.c b/geanylua/glspi_doc.c
index 02543eab1..7a012416b 100644
--- a/geanylua/glspi_doc.c
+++ b/geanylua/glspi_doc.c
@@ -43,6 +43,7 @@ static gint glspi_newfile(lua_State* L)
 		} else {
 			ft=filetypes_lookup_by_name(tmp);
 		}
+		/* Fallthrough */
 	default:
 		if (!lua_isstring(L, 1))	{ return FAIL_STRING_ARG(1); }
 		fn=lua_tostring(L, 1);
@@ -102,7 +103,7 @@ static gint glspi_activate(lua_State* L)
 				}
 			} else if (lua_idx > 0) {
 				/* Positive number refers to the geany->documents_array index */
-				gint doc_idx = lua_idx - 1;
+				guint doc_idx = (guint) (lua_idx - 1);
 				if ((doc_idx < geany->documents_array->len) && documents[doc_idx]->is_valid) {
 					tab_idx = document_get_notebook_page(documents[doc_idx]);
 				}
@@ -208,11 +209,16 @@ static gint glspi_save(lua_State* L)
 	} else {
 		if (lua_isnumber(L,1)) {
 			gint idx=(gint)lua_tonumber(L,1)-1;
-			status=document_save_file(documents[idx], TRUE);
+			GeanyDocument *doc = document_index(idx);
+			if (DOC_VALID(doc)) {
+				status=document_save_file(doc, TRUE);
+			}
 		} else {
 			if (lua_isstring(L,1)) {
 				gint idx=filename_to_doc_idx(lua_tostring(L,1));
-				status=document_save_file(documents[idx], TRUE);
+				if (idx >= 0) {
+					status=document_save_file(documents[idx], TRUE);
+				}
 			} else { return FAIL_STR_OR_NUM_ARG(1);	}
 		}
 	}
@@ -241,7 +247,10 @@ static gint glspi_open(lua_State* L)
 		}
 	}
 	if (!fn) {
-		status=document_reload_force(documents[idx],NULL) ? idx : -1;
+		GeanyDocument*doc=document_index(idx);
+		if (DOC_VALID(doc)) {
+			status=document_reload_force(doc,NULL) ? idx : -1;
+		}
 	} else {
 		guint len=geany->documents_array->len;
 		GeanyDocument*doc=document_open_file(fn,FALSE,NULL,NULL);
@@ -268,12 +277,17 @@ static gint glspi_close(lua_State* L)
 		status=document_close(document_get_current());
 	} else {
 		if (lua_isnumber(L,1)) {
-			guint idx=(guint)lua_tonumber(L,1)-1;
-			status=document_close(documents[idx]);
+			gint idx=(gint)lua_tonumber(L,1)-1;
+			GeanyDocument *doc = document_index(idx);
+			if (DOC_VALID(doc)) {
+				status=document_close(doc);
+			}
 		} else {
 			if (lua_isstring(L,1)) {
-				guint idx=(guint)filename_to_doc_idx(lua_tostring(L,1));
-				status=document_close(documents[idx]);
+				gint idx=filename_to_doc_idx(lua_tostring(L,1));
+				if (idx >= 0) {
+					status=document_close(documents[idx]);
+				}
 			} else { return FAIL_STR_OR_NUM_ARG(1);	}
 		}
 	}
diff --git a/geanylua/glspi_sci.c b/geanylua/glspi_sci.c
index f07fa3521..fc3d69835 100644
--- a/geanylua/glspi_sci.c
+++ b/geanylua/glspi_sci.c
@@ -392,9 +392,11 @@ static gint glspi_navigate(lua_State* L)
 		case 4:
 			if (!lua_isboolean(L,4)) { return FAIL_BOOL_ARG(4); }
 			rect=lua_toboolean(L,4);
+			/* Fallthrough */
 		case 3:
 			if (!lua_isboolean(L,3)) { return FAIL_BOOL_ARG(3); }
 			sel=lua_toboolean(L,3);
+			/* Fallthrough */
 		case 2:
 			if (!lua_isnumber(L,2)) { return FAIL_NUMERIC_ARG(2); }
 			count=lua_tonumber(L,2);
@@ -402,6 +404,7 @@ static gint glspi_navigate(lua_State* L)
 				fwd=FALSE;
 				count=0-count;
 			}
+			/* Fallthrough */
 		case 1:
 			if (!lua_isstring(L,1)) { return FAIL_STRING_ARG(1); }
 			strcmd=lua_tostring(L,1);