diff --git a/src/libCom/ellLib/ellLib.h b/src/libCom/ellLib/ellLib.h
index 300a2df3f..52b58d169 100644
--- a/src/libCom/ellLib/ellLib.h
+++ b/src/libCom/ellLib/ellLib.h
@@ -56,7 +56,7 @@ epicsShareFunc void ellInsert (ELLLIST *plist, ELLNODE *pPrev, ELLNODE *pNode);
 epicsShareFunc ELLNODE * ellNth (ELLLIST *pList, int nodeNum);
 epicsShareFunc ELLNODE * ellNStep (ELLNODE *pNode, int nStep);
 epicsShareFunc int  ellFind (ELLLIST *pList, ELLNODE *pNode);
-typedef int (*pListCmp)(ELLNODE* A, ELLNODE* B);
+typedef int (*pListCmp)(const ELLNODE* A, const ELLNODE* B);
 epicsShareFunc void ellSortStable(ELLLIST *pList, pListCmp);
 epicsShareFunc void ellFree2 (ELLLIST *pList, FREEFUNC freeFunc);
 epicsShareFunc void ellVerify (ELLLIST *pList);
diff --git a/src/libCom/test/epicsEllTest.c b/src/libCom/test/epicsEllTest.c
index 78c695466..62ee14e39 100644
--- a/src/libCom/test/epicsEllTest.c
+++ b/src/libCom/test/epicsEllTest.c
@@ -196,7 +196,7 @@ static void testList(void)
 
 typedef struct { int A, B; } input_t;
 
-static int myItemCmp(ELLNODE *a, ELLNODE *b)
+static int myItemCmp(const ELLNODE *a, const ELLNODE *b)
 {
     struct myItem *A = CONTAINER(a, struct myItem, node),
                   *B = CONTAINER(b, struct myItem, node);