diff --git a/src/internal.c b/src/internal.c
index 080ded6f..7fcc07f0 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -3988,6 +3988,9 @@ static word32 AlgoListSz(const char* algoList)
 {
     word32 algoListSz;
 
+    if (algoList == NULL)
+        return 0;
+
     algoListSz = (word32)WSTRLEN(algoList);
     if (algoList[algoListSz-1] == ',') {
         --algoListSz;