diff --git a/src/libCom/misc/truncateFile.c b/src/libCom/misc/truncateFile.c
index 9ff2455ec..ccb1450c2 100644
--- a/src/libCom/misc/truncateFile.c
+++ b/src/libCom/misc/truncateFile.c
@@ -25,7 +25,7 @@
  * truncate to specified size (we dont use truncate()
  * because it is not portable)
  */
-epicsShareFunc enum TF_RETURN  truncateFile (const char *pFileName, unsigned size)
+epicsShareFunc enum TF_RETURN  truncateFile (const char *pFileName, unsigned long size)
 {
 	char tmpName[256>L_tmpnam?256:L_tmpnam];
 	long filePos;
diff --git a/src/libCom/osi/epicsStdio.h b/src/libCom/osi/epicsStdio.h
index d05a6912a..172d5cf87 100644
--- a/src/libCom/osi/epicsStdio.h
+++ b/src/libCom/osi/epicsStdio.h
@@ -66,7 +66,7 @@ epicsShareFunc int epicsShareAPI epicsVsnprintf(
  * TF_ERROR if the file could not be truncated.
  */
 enum TF_RETURN {TF_OK=0, TF_ERROR=1};
-epicsShareFunc enum TF_RETURN truncateFile ( const char *pFileName, unsigned size );
+epicsShareFunc enum TF_RETURN truncateFile ( const char *pFileName, unsigned long size );
 
 /* The following are for redirecting stdin,stdout,stderr */
 epicsShareFunc FILE * epicsShareAPI epicsGetStdin(void);