diff --git a/src/as/Makefile b/src/as/Makefile
index 3f7196d6d..20d771645 100644
--- a/src/as/Makefile
+++ b/src/as/Makefile
@@ -20,7 +20,6 @@ LIB_SRCS += asTrapWrite.c
 
 asIoc_SRCS += asDbLib.c
 asIoc_SRCS += asCa.c
-asIoc_SRCS += asTrapWrite.c
 
 LIBRARY_HOST = asHost
 LIBRARY_IOC = asIoc
diff --git a/src/as/asLib.h b/src/as/asLib.h
index fc8307288..faf35f355 100644
--- a/src/as/asLib.h
+++ b/src/as/asLib.h
@@ -81,7 +81,7 @@ epicsShareFunc int epicsShareAPI asDumpMem(char *asgname,void (*memcallback)(ASM
 epicsShareFunc int epicsShareAPI asDumpHash(void);
 
 epicsShareFunc void * epicsShareAPI asTrapWriteBeforeWrite(
-    char *userid,char *hostid,void *addr);
+    const char *userid,const char *hostid,void *addr);
 
 epicsShareFunc void epicsShareAPI asTrapWriteAfterWrite(void *pvt);
 
diff --git a/src/as/asTrapWrite.c b/src/as/asTrapWrite.c
index 0b4216f07..29a7f92ff 100644
--- a/src/as/asTrapWrite.c
+++ b/src/as/asTrapWrite.c
@@ -111,7 +111,7 @@ void epicsShareAPI asTrapWriteUnregisterListener(asTrapWriteId id)
 }
 
 void * epicsShareAPI asTrapWriteBeforeWrite(
-    char *userid,char *hostid,void *addr)
+    const char *userid,const char *hostid,void *addr)
 {
     writeMessage *pwriteMessage;
     listener *plistener;
diff --git a/src/as/asTrapWrite.h b/src/as/asTrapWrite.h
index 4c28bb634..ec34c5312 100644
--- a/src/as/asTrapWrite.h
+++ b/src/as/asTrapWrite.h
@@ -20,8 +20,8 @@ extern "C" {
 #endif
 
 typedef struct asTrapWriteMessage {
-    char *userid;
-    char *hostid;
+    const char *userid;
+    const char *hostid;
     void *serverSpecific;
     void *userPvt;
 } asTrapWriteMessage;