diff --git a/error.c b/error.c
index ce1b0401..d7d792d5 100644
--- a/error.c
+++ b/error.c
@@ -55,7 +55,7 @@ SR_API const char *sr_strerror(int error_code)
 	const char *str;
 
 	/*
-	 * Note: All defined SR_* error macros from libsigrok.h should have
+	 * Note: All defined SR_* error macros from libsigrok.h must have
 	 * an entry in this function, as well as in sr_strerror_name().
 	 */
 
@@ -81,6 +81,9 @@ SR_API const char *sr_strerror(int error_code)
 	case SR_ERR_NA:
 		str = "not applicable";
 		break;
+	case SR_ERR_DEV_CLOSED:
+		str = "device closed but should be open";
+		break;
 	default:
 		str = "unknown error";
 		break;
@@ -112,7 +115,7 @@ SR_API const char *sr_strerror_name(int error_code)
 	const char *str;
 
 	/*
-	 * Note: All defined SR_* error macros from libsigrok.h should have
+	 * Note: All defined SR_* error macros from libsigrok.h must have
 	 * an entry in this function, as well as in sr_strerror().
 	 */
 
@@ -138,6 +141,9 @@ SR_API const char *sr_strerror_name(int error_code)
 	case SR_ERR_NA:
 		str = "SR_ERR_NA";
 		break;
+	case SR_ERR_DEV_CLOSED:
+		str = "SR_ERR_DEV_CLOSED";
+		break;
 	default:
 		str = "unknown error code";
 		break;
diff --git a/libsigrok.h b/libsigrok.h
index 24934baa..79a76771 100644
--- a/libsigrok.h
+++ b/libsigrok.h
@@ -72,6 +72,11 @@ enum {
 	SR_ERR_SAMPLERATE = -5, /**< Incorrect samplerate. */
 	SR_ERR_NA         = -6, /**< Not applicable. */
 	SR_ERR_DEV_CLOSED = -7, /**< Device is closed, but needs to be open. */
+
+	/*
+	 * Note: When adding entries here, don't forget to also update the
+	 * sr_strerror() and sr_strerror_name() functions in error.c.
+	 */
 };
 
 #define SR_MAX_NUM_PROBES    64 /* Limited by uint64_t. */