diff --git a/src/51d.c b/src/51d.c
index 7017095..c87525d 100644
--- a/src/51d.c
+++ b/src/51d.c
@@ -702,7 +702,8 @@
 
 	free(global_51degrees.header_names);
 #ifdef FIFTYONEDEGREES_H_PATTERN_INCLUDED
-	fiftyoneDegreesWorksetPoolFree(global_51degrees.pool);
+	if (global_51degrees.pool)
+		fiftyoneDegreesWorksetPoolFree(global_51degrees.pool);
 #endif
 #ifdef FIFTYONEDEGREES_H_TRIE_INCLUDED
 #ifdef FIFTYONEDEGREES_NO_THREADING