diff --git a/src/core/vsprintf.c b/src/core/vsprintf.c
index e6f072e7..4457fe4f 100644
--- a/src/core/vsprintf.c
+++ b/src/core/vsprintf.c
@@ -338,6 +338,45 @@ int snprintf ( char *buf, size_t size, const char *fmt, ... ) {
 	return i;
 }
 
+/**
+ * Version of vsnprintf() that accepts a signed buffer size
+ *
+ * @v buf		Buffer into which to write the string
+ * @v size		Size of buffer
+ * @v fmt		Format string
+ * @v args		Arguments corresponding to the format string
+ * @ret len		Length of formatted string
+ */
+int vssnprintf ( char *buf, ssize_t ssize, const char *fmt, va_list args ) {
+
+	/* Treat negative buffer size as zero buffer size */
+	if ( ssize < 0 )
+		ssize = 0;
+
+	/* Hand off to vsnprintf */
+	return vsnprintf ( buf, ssize, fmt, args );
+}
+
+/**
+ * Version of vsnprintf() that accepts a signed buffer size
+ *
+ * @v buf		Buffer into which to write the string
+ * @v size		Size of buffer
+ * @v fmt		Format string
+ * @v ...		Arguments corresponding to the format string
+ * @ret len		Length of formatted string
+ */
+int ssnprintf ( char *buf, ssize_t ssize, const char *fmt, ... ) {
+	va_list args;
+	int len;
+
+	/* Hand off to vssnprintf */
+	va_start ( args, fmt );
+	len = vssnprintf ( buf, ssize, fmt, args );
+	va_end ( args );
+	return len;
+}
+
 /**
  * Write character to console
  *
diff --git a/src/include/gpxe/vsprintf.h b/src/include/gpxe/vsprintf.h
index ac87c5a8..9360f29b 100644
--- a/src/include/gpxe/vsprintf.h
+++ b/src/include/gpxe/vsprintf.h
@@ -64,4 +64,8 @@ struct printf_context {
 
 extern size_t vcprintf ( struct printf_context *ctx, const char *fmt,
 			 va_list args );
+extern int vssnprintf ( char *buf, ssize_t ssize, const char *fmt,
+			va_list args );
+extern int ssnprintf ( char *buf, ssize_t ssize, const char *fmt, ... );
+
 #endif /* _GPXE_VSPRINTF_H */
diff --git a/src/net/tcp/iscsi.c b/src/net/tcp/iscsi.c
index 56567976..f95286d0 100644
--- a/src/net/tcp/iscsi.c
+++ b/src/net/tcp/iscsi.c
@@ -23,6 +23,7 @@
 #include <errno.h>
 #include <assert.h>
 #include <byteswap.h>
+#include <gpxe/vsprintf.h>
 #include <gpxe/scsi.h>
 #include <gpxe/process.h>
 #include <gpxe/uaccess.h>
@@ -348,32 +349,6 @@ static void iscsi_tx_data_out ( struct iscsi_session *iscsi,
  *
  */
 
-/**
- * Version of snprintf() that accepts a signed buffer size
- *
- * @v buf		Buffer into which to write the string
- * @v size		Size of buffer
- * @v fmt		Format string
- * @v args		Arguments corresponding to the format string
- * @ret len		Length of formatted string
- *
- * This is a utility function for iscsi_build_login_request_strings().
- */
-static int ssnprintf ( char *buf, ssize_t ssize, const char *fmt, ... ) {
-	va_list args;
-	int len;
-
-	/* Treat negative buffer size as zero buffer size */
-	if ( ssize < 0 )
-		ssize = 0;
-
-	/* Hand off to vsnprintf */
-	va_start ( args, fmt );
-	len = vsnprintf ( buf, ssize, fmt, args );
-	va_end ( args );
-	return len;
-}
-
 /**
  * Build iSCSI login request strings
  *