diff --git a/lib/database-private.h b/lib/database-private.h
index 8b9d67fe..8dd77281 100644
--- a/lib/database-private.h
+++ b/lib/database-private.h
@@ -190,6 +190,39 @@ operator& (notmuch_field_flag_t a, notmuch_field_flag_t b)
 				    Xapian::QueryParser::FLAG_WILDCARD | \
 				    Xapian::QueryParser::FLAG_PURE_NOT)
 
+/*
+ * Which parameters were explicit when the database was opened */
+typedef enum {
+    NOTMUCH_PARAM_NONE		= 0,
+    NOTMUCH_PARAM_DATABASE	= 1 << 0,
+    NOTMUCH_PARAM_CONFIG	= 1 << 1,
+    NOTMUCH_PARAM_PROFILE	= 1 << 2,
+} notmuch_open_param_t;
+
+/*
+ * define bitwise operators to hide casts */
+
+inline notmuch_open_param_t
+operator| (notmuch_open_param_t a, notmuch_open_param_t b)
+{
+    return static_cast<notmuch_open_param_t>(
+	static_cast<unsigned>(a) | static_cast<unsigned>(b));
+}
+
+inline notmuch_open_param_t&
+operator|= (notmuch_open_param_t &a, notmuch_open_param_t b)
+{
+    a = a | b;
+    return a;
+}
+
+inline notmuch_open_param_t
+operator& (notmuch_open_param_t a, notmuch_open_param_t b)
+{
+    return static_cast<notmuch_open_param_t>(
+	static_cast<unsigned>(a) & static_cast<unsigned>(b));
+}
+
 struct _notmuch_database {
     bool exception_reported;
 
@@ -249,6 +282,9 @@ struct _notmuch_database {
 
     /* Cached and possibly overridden configuration */
     notmuch_string_map_t *config;
+
+    /* Track what parameters were specified when opening */
+    notmuch_open_param_t params;
 };
 
 /* Prior to database version 3, features were implied by the database
diff --git a/lib/open.cc b/lib/open.cc
index ba32c2f1..a942383b 100644
--- a/lib/open.cc
+++ b/lib/open.cc
@@ -247,7 +247,7 @@ _choose_database_path (void *ctx,
 }
 
 static notmuch_database_t *
-_alloc_notmuch ()
+_alloc_notmuch (const char *database_path, const char *config_path, const char *profile)
 {
     notmuch_database_t *notmuch;
 
@@ -263,6 +263,15 @@ _alloc_notmuch ()
     notmuch->transaction_count = 0;
     notmuch->transaction_threshold = 0;
     notmuch->view = 1;
+
+    notmuch->params = NOTMUCH_PARAM_NONE;
+    if (database_path)
+	notmuch->params |= NOTMUCH_PARAM_DATABASE;
+    if (config_path)
+	notmuch->params |= NOTMUCH_PARAM_CONFIG;
+    if (profile)
+	notmuch->params |= NOTMUCH_PARAM_PROFILE;
+
     return notmuch;
 }
 
@@ -510,7 +519,7 @@ notmuch_database_open_with_config (const char *database_path,
 
     _notmuch_init ();
 
-    notmuch = _alloc_notmuch ();
+    notmuch = _alloc_notmuch (database_path, config_path, profile);
     if (! notmuch) {
 	status = NOTMUCH_STATUS_OUT_OF_MEMORY;
 	goto DONE;
@@ -610,7 +619,7 @@ notmuch_database_create_with_config (const char *database_path,
 
     _notmuch_init ();
 
-    notmuch = _alloc_notmuch ();
+    notmuch = _alloc_notmuch (database_path, config_path, profile);
     if (! notmuch) {
 	status = NOTMUCH_STATUS_OUT_OF_MEMORY;
 	goto DONE;
@@ -812,7 +821,7 @@ notmuch_database_load_config (const char *database_path,
 
     _notmuch_init ();
 
-    notmuch = _alloc_notmuch ();
+    notmuch = _alloc_notmuch (database_path, config_path, profile);
     if (! notmuch) {
 	status = NOTMUCH_STATUS_OUT_OF_MEMORY;
 	goto DONE;