diff --git a/src/space.c b/src/space.c
index be0aed8..89905c6 100644
--- a/src/space.c
+++ b/src/space.c
@@ -803,10 +803,16 @@ void planets_render(void) {
 // Clean up the system.
 void space_exit(void) {
   int i,j;
-
+  
   // Free the names.
-  if(planetname_stack) free(planetname_stack);
-  if(systemname_stack) free(systemname_stack);
+  if(planetname_stack) {
+  	 free(planetname_stack);
+  	 planetname_stack = NULL;
+  }
+  if(systemname_stack) {
+   free(systemname_stack);
+   systemname_stack = NULL;
+  }
   spacename_nstack = 0;
 
   // Free the systems.