diff --git a/lib/Makefile.am b/lib/Makefile.am
index 7da50fba01555c464db783cdf23b8cfae4193c90..a42823bddd77731659ec3b8456529e6dbb616742 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -42,7 +42,8 @@ OBJECTS = \
 	ngtcp2_pq.c \
 	ngtcp2_rob.c \
 	ngtcp2_ppe.c \
-	ngtcp2_crypto.c
+	ngtcp2_crypto.c \
+	ngtcp2_err.c
 
 HFILES = \
 	ngtcp2_pkt.h \
@@ -56,6 +57,7 @@ HFILES = \
 	ngtcp2_rob.h \
 	ngtcp2_ppe.h \
 	ngtcp2_crypto.h \
+	ngtcp2_err.h \
 	ngtcp2_macro.h
 
 libngtcp2_la_SOURCES = $(HFILES) $(OBJECTS)
diff --git a/lib/includes/ngtcp2/ngtcp2.h b/lib/includes/ngtcp2/ngtcp2.h
index e3082f38988007e5d1421a6c2907c3dbe64f9e79..4683061d675f564a2039fa8081a93549333af7a6 100644
--- a/lib/includes/ngtcp2/ngtcp2.h
+++ b/lib/includes/ngtcp2/ngtcp2.h
@@ -594,6 +594,13 @@ NGTCP2_EXTERN int ngtcp2_conn_update_rx_keys(ngtcp2_conn *conn,
                                              const uint8_t *key, size_t keylen,
                                              const uint8_t *iv, size_t ivlen);
 
+/**
+ * @function
+ *
+ * `ngtcp2_strerror` returns the text representation of |liberr|.
+ */
+NGTCP2_EXTERN const char *ngtcp2_strerror(int liberr);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/ngtcp2_err.c b/lib/ngtcp2_err.c
new file mode 100644
index 0000000000000000000000000000000000000000..5490213f3caf521212a37e682d79b045b038e292
--- /dev/null
+++ b/lib/ngtcp2_err.c
@@ -0,0 +1,50 @@
+/*
+ * ngtcp2
+ *
+ * Copyright (c) 2017 ngtcp2 contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "ngtcp2_err.h"
+
+const char *ngtcp2_strerror(int liberr) {
+  switch (liberr) {
+  case NGTCP2_ERR_INVALID_ARGUMENT:
+    return "ERR_INVALID_ARGUMENT";
+  case NGTCP2_ERR_UNKNOWN_PKT_TYPE:
+    return "ERR_UNKNOWN_PKT_TYPE";
+  case NGTCP2_ERR_NOBUF:
+    return "ERR_NOBUF";
+  case NGTCP2_ERR_BAD_PKT_HASH:
+    return "ERR_BAD_PKT_HASH";
+  case NGTCP2_ERR_PROTO:
+    return "ERR_PROTO";
+  case NGTCP2_ERR_INVALID_STATE:
+    return "ERR_INVALID_STATE";
+  case NGTCP2_ERR_NOMEM:
+    return "ERR_NOMEM";
+  case NGTCP2_ERR_CALLBACK_FAILURE:
+    return "ERR_CALLBACK_FAILURE";
+  case NGTCP2_ERR_INTERNAL:
+    return "ERR_INTERNAL";
+  default:
+    return "UNKNOWN";
+  }
+}
diff --git a/lib/ngtcp2_err.h b/lib/ngtcp2_err.h
new file mode 100644
index 0000000000000000000000000000000000000000..e950915153df46bc86bc5a86fd3ca65b89e0ce0b
--- /dev/null
+++ b/lib/ngtcp2_err.h
@@ -0,0 +1,34 @@
+/*
+ * ngtcp2
+ *
+ * Copyright (c) 2017 ngtcp2 contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef NGTCP2_ERR_H
+#define NGTCP2_ERR_H
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif /* HAVE_CONFIG_H */
+
+#include <ngtcp2/ngtcp2.h>
+
+#endif /* NGTCP2_ERR_H */