diff --git a/src/matrix-http-api.c b/src/matrix-http-api.c
index 5eefe1a..3008dd2 100644
--- a/src/matrix-http-api.c
+++ b/src/matrix-http-api.c
@@ -637,7 +637,7 @@ _response_callback(SoupSession *session,
 
                             if (strncmp("M_", errcode, 2) == 0) {
                                 gchar *matrix_error_code = g_strdup_printf(
-                                        "MATRIX_ERROR_%s", errcode + 2);
+                                        "MATRIX_ERROR_%s", errcode);
 
                                 error_class = g_type_class_ref(
                                         MATRIX_TYPE_ERROR);
@@ -2314,7 +2314,7 @@ i_token_refresh(MatrixAPI *api,
 
     if (!refresh_token && !priv->refresh_token) {
         g_set_error(error,
-                    MATRIX_ERROR, MATRIX_ERROR_MISSING_TOKEN,
+                    MATRIX_ERROR, MATRIX_ERROR_M_MISSING_TOKEN,
                     "No token available");
 
         return;
diff --git a/src/matrix-http-client.c b/src/matrix-http-client.c
index 510860e..06dc2b2 100644
--- a/src/matrix-http-client.c
+++ b/src/matrix-http-client.c
@@ -166,7 +166,7 @@ cb_event_stream(MatrixAPI *api,
     // Only continue polling if polling is still enabled, and there
     // was no communication error during the last call
     if (priv->polling
-        && (!error || error->code <= MATRIX_ERROR_MISSING_TOKEN)) {
+        && (!error || error->code <= MATRIX_ERROR_M_MISSING_TOKEN)) {
         priv->polling = FALSE;
 
         matrix_api_event_stream(api,
diff --git a/src/matrix-types.c b/src/matrix-types.c
index ed2e14c..1d43a0e 100644
--- a/src/matrix-types.c
+++ b/src/matrix-types.c
@@ -45,19 +45,21 @@
  *                              server contains a value unknown to
  *                              this library. These should be reported
  *                              to the Matrix GLib SDK developers
- * @MATRIX_ERROR_MISSING_TOKEN: authorization token is missing from
- *                              the request
- * @MATRIX_ERROR_FORBIDDEN: access was forbidden (e.g. due to a
- *                          missing/invalid token, or using a bad
- *                          password during login)
- * @MATRIX_ERROR_UNKNOWN: an error unknown to the Matrix homeserver
- * @MATRIX_ERROR_UNKNOWN_TOKEN: the token provided is not known for
- *                              the homeserver
- * @MATRIX_ERROR_NOT_JSON: illegal request, the content is not valid
- *                         JSON
- * @MATRIX_ERROR_UNRECOGNIZED: the homeserver didn't understand the
- *                             request
- * @MATRIX_ERROR_UNSPECIFIED: no error code was sent by the homeserver
+ * @MATRIX_ERROR_M_MISSING_TOKEN: authorization token is missing from
+ *                                the request
+ * @MATRIX_ERROR_M_FORBIDDEN: access was forbidden (e.g. due to a
+ *                            missing/invalid token, or using a bad
+ *                            password during login)
+ * @MATRIX_ERROR_M_UNKNOWN: an error unknown to the Matrix homeserver
+ * @MATRIX_ERROR_M_UNKNOWN_TOKEN: the token provided is not known for
+ *                                the homeserver
+ * @MATRIX_ERROR_M_NOT_JSON: illegal request, the content is not valid
+ *                           JSON
+ * @MATRIX_ERROR_M_UNRECOGNIZED: the homeserver didn't understand the
+ *                               request
+ * @MATRIX_ERROR_UNSPECIFIED: no error code was sent by the
+ *                            homeserver. If you see this error, that
+ *                            usually indicates a homeserver bug
  * @MATRIX_ERROR_UNKNOWN_ERROR: an error unknown to this library
  *
  * Value mappings from Matrix.org API error codes
diff --git a/src/matrix-types.h b/src/matrix-types.h
index 59123c3..43b6f65 100644
--- a/src/matrix-types.h
+++ b/src/matrix-types.h
@@ -33,15 +33,15 @@ typedef enum {
     MATRIX_ERROR_INVALID_ROOM_ID,
     MATRIX_ERROR_UNKNOWN_VALUE,
 
-    /* Add Matrix-defined error codes under here, changing `M_` to
-     * `MATRIX_ERROR`, i.e. `M_FORBIDDEN` =>
-     * `MATRIX_ERROR_FORBIDDEN` */
-    MATRIX_ERROR_MISSING_TOKEN = 500,
-    MATRIX_ERROR_FORBIDDEN,
-    MATRIX_ERROR_UNKNOWN,
-    MATRIX_ERROR_UNKNOWN_TOKEN,
-    MATRIX_ERROR_NOT_JSON,
-    MATRIX_ERROR_UNRECOGNIZED,
+    /* Add Matrix-defined error codes under here, prefixing them with
+     * `MATRIX_ERROR_`, i.e. `M_FORBIDDEN` =>
+     * `MATRIX_ERROR_M_FORBIDDEN` */
+    MATRIX_ERROR_M_MISSING_TOKEN = 500,
+    MATRIX_ERROR_M_FORBIDDEN,
+    MATRIX_ERROR_M_UNKNOWN,
+    MATRIX_ERROR_M_UNKNOWN_TOKEN,
+    MATRIX_ERROR_M_NOT_JSON,
+    MATRIX_ERROR_M_UNRECOGNIZED,
 
     /* Allow for a lot of Matrix.org defined codes
        Do not define error codes after this! */