diff --git a/lib/isc/win32/stdio.c b/lib/isc/win32/stdio.c
index 50e473835e..6f65fdbf7e 100644
--- a/lib/isc/win32/stdio.c
+++ b/lib/isc/win32/stdio.c
@@ -23,6 +23,7 @@
 #include <errno.h>
 
 #include <isc/stdio.h>
+#include <isc/util.h>
 
 #include "errno2result.h"
 
@@ -63,6 +64,28 @@ isc_stdio_seek(FILE *f, off_t offset, int whence) {
 		return (isc__errno2result(errno));
 }
 
+isc_result_t
+isc_stdio_tell(FILE *f, off_t *offsetp) {
+#ifndef _WIN64
+	long r;
+#else
+	__int64 r;
+#endif
+
+	REQUIRE(offsetp != NULL);
+
+#ifndef _WIN64
+	r = ftell(f);
+#else
+	r = _ftelli64(f);
+#endif
+	if (r >= 0) {
+		*offsetp = r;
+		return (ISC_R_SUCCESS);
+	} else
+		return (isc__errno2result(errno));
+}
+
 isc_result_t
 isc_stdio_read(void *ptr, size_t size, size_t nmemb, FILE *f, size_t *nret) {
 	isc_result_t result = ISC_R_SUCCESS;