diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index ce532e9e07..7c7f57874a 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -12731,8 +12731,29 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 				RememberConstraintForRebuilding(foundObject.objectId, tab);
 				break;
 
+			case OCLASS_PROC:
+
+				/*
+				 * A new-style SQL function can depend on a column, if that
+				 * column is referenced in the parsed function body.  Ideally
+				 * we'd automatically update the function by deparsing and
+				 * reparsing it, but that's risky and might well fail anyhow.
+				 * FIXME someday.
+				 */
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("cannot alter type of a column used by a function or procedure"),
+						 errdetail("%s depends on column \"%s\"",
+								   getObjectDescription(&foundObject, false),
+								   colName)));
+				break;
+
 			case OCLASS_REWRITE:
-				/* XXX someday see if we can cope with revising views */
+
+				/*
+				 * View/rule bodies have pretty much the same issues as
+				 * function bodies.  FIXME someday.
+				 */
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 						 errmsg("cannot alter type of a column used by a view or rule"),
@@ -12748,9 +12769,9 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 				 * specified as an update target, or because the column is
 				 * used in the trigger's WHEN condition.  The first case would
 				 * not require any extra work, but the second case would
-				 * require updating the WHEN expression, which will take a
-				 * significant amount of new code.  Since we can't easily tell
-				 * which case applies, we punt for both.  FIXME someday.
+				 * require updating the WHEN expression, which has the same
+				 * issues as above.  Since we can't easily tell which case
+				 * applies, we punt for both.  FIXME someday.
 				 */
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -12822,7 +12843,6 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 				RememberStatisticsForRebuilding(foundObject.objectId, tab);
 				break;
 
-			case OCLASS_PROC:
 			case OCLASS_TYPE:
 			case OCLASS_CAST:
 			case OCLASS_COLLATION: