diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 3556240c8ed..f1725c9da8c 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -45,6 +45,7 @@
 #include "catalog/pg_namespace.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_policy.h"
+#include "catalog/pg_proc.h"
 #include "catalog/pg_rewrite.h"
 #include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_tablespace.h"
@@ -14094,8 +14095,33 @@ RememberAllDependentForRebuilding(AlteredTableInfo *tab, AlterTableType subtype,
 				RememberConstraintForRebuilding(foundObject.objectId, tab);
 				break;
 
+			case ProcedureRelationId:
+
+				/*
+				 * 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.
+				 *
+				 * This is only a problem for AT_AlterColumnType, not
+				 * AT_SetExpression.
+				 */
+				if (subtype == AT_AlterColumnType)
+					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 RewriteRelationId:
-				/* XXX someday see if we can cope with revising views */
+
+				/*
+				 * View/rule bodies have pretty much the same issues as
+				 * function bodies.  FIXME someday.
+				 */
 				if (subtype == AT_AlterColumnType)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -14112,9 +14138,9 @@ RememberAllDependentForRebuilding(AlteredTableInfo *tab, AlterTableType subtype,
 				 * 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.
 				 */
 				if (subtype == AT_AlterColumnType)
 					ereport(ERROR,