diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 1dbd014..82e9c57 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -1544,6 +1544,9 @@
     int		is_fish_shell;
     char_u	*shell_name = get_isolated_shell_name();
 
+    if (shell_name == NULL)
+	return NULL;
+
     // Account for fish's different syntax for subshells
     is_fish_shell = (fnamecmp(shell_name, "fish") == 0);
     vim_free(shell_name);