diff --git a/src/md_result.c b/src/md_result.c

index 4076d5b..0e0b688 100644

--- a/src/md_result.c

+++ b/src/md_result.c

@@ -32,7 +32,7 @@

 static const char *dup_trim(apr_pool_t *p, const char *s)

 {

     char *d = apr_pstrdup(p, s);

-    apr_collapse_spaces(d, d);

+    if (d) apr_collapse_spaces(d, d);

     return d;

 }