diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index ca3a162bbfa..12355348c95 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -205,19 +205,22 @@ do { \
 	matches = completion_matches(text, complete_from_versioned_schema_query); \
 } while (0)
 
+/*
+ * Caution: COMPLETE_WITH_CONST is not for general-purpose use; you probably
+ * want COMPLETE_WITH() with one element, instead.
+ */
+#define COMPLETE_WITH_CONST(cs, con) \
+do { \
+	completion_case_sensitive = (cs); \
+	completion_charp = (con); \
+	matches = completion_matches(text, complete_from_const); \
+} while (0)
+
 #define COMPLETE_WITH_LIST_INT(cs, list) \
 do { \
 	completion_case_sensitive = (cs); \
-	if (!(list)[1]) \
-	{ \
-		completion_charp = (list)[0]; \
-		matches = completion_matches(text, complete_from_const); \
-	} \
-	else \
-	{ \
-		completion_charpp = (list); \
-		matches = completion_matches(text, complete_from_list); \
-	} \
+	completion_charpp = (list); \
+	matches = completion_matches(text, complete_from_list); \
 } while (0)
 
 #define COMPLETE_WITH_LIST(list) COMPLETE_WITH_LIST_INT(false, list)
@@ -3758,7 +3761,7 @@ psql_completion(const char *text, int start, int end)
 	 */
 	if (matches == NULL)
 	{
-		COMPLETE_WITH("");
+		COMPLETE_WITH_CONST(true, "");
 #ifdef HAVE_RL_COMPLETION_APPEND_CHARACTER
 		rl_completion_append_character = '\0';
 #endif
@@ -4188,10 +4191,21 @@ complete_from_list(const char *text, int state)
 
 /*
  * This function returns one fixed string the first time even if it doesn't
- * match what's there, and nothing the second time. This should be used if
- * there is only one possibility that can appear at a certain spot, so
- * misspellings will be overwritten.  The string to be passed must be in
- * completion_charp.
+ * match what's there, and nothing the second time.  The string
+ * to be used must be in completion_charp.
+ *
+ * If the given string is "", this has the effect of preventing readline
+ * from doing any completion.  (Without this, readline tries to do filename
+ * completion which is seldom the right thing.)
+ *
+ * If the given string is not empty, readline will replace whatever the
+ * user typed with that string.  This behavior might be useful if it's
+ * completely certain that we know what must appear at a certain spot,
+ * so that it's okay to overwrite misspellings.  In practice, given the
+ * relatively lame parsing technology used in this file, the level of
+ * certainty is seldom that high, so that you probably don't want to
+ * use this.  Use complete_from_list with a one-element list instead;
+ * that won't try to auto-correct "misspellings".
  */
 static char *
 complete_from_const(const char *text, int state)