diff --git a/src/tools/pg_bsd_indent/indent.c b/src/tools/pg_bsd_indent/indent.c
index 1a29409173b..138a13063a7 100644
--- a/src/tools/pg_bsd_indent/indent.c
+++ b/src/tools/pg_bsd_indent/indent.c
@@ -536,7 +536,7 @@ check_type:
 	case lparen:		/* got a '(' or '[' */
 	    /* count parens to make Healy happy */
 	    if (++ps.p_l_follow == nitems(ps.paren_indents)) {
-		diag3(0, "Reached internal limit of %d unclosed parens",
+		diag3(0, "Reached internal limit of %zu unclosed parens",
 		    nitems(ps.paren_indents));
 		ps.p_l_follow--;
 	    }
@@ -809,7 +809,7 @@ check_type:
 						 * declaration or an init */
 		di_stack[ps.dec_nest] = dec_ind;
 		if (++ps.dec_nest == nitems(di_stack)) {
-		    diag3(0, "Reached internal limit of %d struct levels",
+		    diag3(0, "Reached internal limit of %zu struct levels",
 			nitems(di_stack));
 		    ps.dec_nest--;
 		}
diff --git a/src/tools/pg_bsd_indent/indent.h b/src/tools/pg_bsd_indent/indent.h
index e9e71d667d8..974ffe1ac27 100644
--- a/src/tools/pg_bsd_indent/indent.h
+++ b/src/tools/pg_bsd_indent/indent.h
@@ -39,9 +39,7 @@ int	compute_label_target(void);
 int	count_spaces(int, char *);
 int	count_spaces_until(int, char *, char *);
 int	lexi(struct parser_state *);
-void	diag2(int, const char *);
-void	diag3(int, const char *, int);
-void	diag4(int, const char *, int, int);
+void	diag(int level, const char *msg, ...) pg_attribute_printf(2, 3);
 void	dump_line(void);
 int	lookahead(void);
 void	lookahead_reset(void);
@@ -51,3 +49,8 @@ void	pr_comment(void);
 void	set_defaults(void);
 void	set_option(char *);
 void	set_profile(const char *);
+
+/* backwards-compatibility macros */
+#define diag2(level, msg) diag(level, msg)
+#define diag3(level, msg, a) diag(level, msg, a)
+#define diag4(level, msg, a, b) diag(level, msg, a, b)
diff --git a/src/tools/pg_bsd_indent/io.c b/src/tools/pg_bsd_indent/io.c
index 62d600bbb11..787b3ce6177 100644
--- a/src/tools/pg_bsd_indent/io.c
+++ b/src/tools/pg_bsd_indent/io.c
@@ -553,53 +553,22 @@ count_spaces(int cur, char *buffer)
 }
 
 void
-diag4(int level, const char *msg, int a, int b)
+diag(int level, const char *msg, ...)
 {
+    va_list ap;
+
+    va_start(ap, msg);
     if (level)
 	found_err = 1;
     if (output == stdout) {
 	fprintf(stdout, "/**INDENT** %s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stdout, msg, a, b);
+	vfprintf(stdout, msg, ap);
 	fprintf(stdout, " */\n");
     }
     else {
 	fprintf(stderr, "%s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stderr, msg, a, b);
+	vfprintf(stderr, msg, ap);
 	fprintf(stderr, "\n");
     }
+    va_end(ap);
 }
-
-void
-diag3(int level, const char *msg, int a)
-{
-    if (level)
-	found_err = 1;
-    if (output == stdout) {
-	fprintf(stdout, "/**INDENT** %s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stdout, msg, a);
-	fprintf(stdout, " */\n");
-    }
-    else {
-	fprintf(stderr, "%s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stderr, msg, a);
-	fprintf(stderr, "\n");
-    }
-}
-
-void
-diag2(int level, const char *msg)
-{
-    if (level)
-	found_err = 1;
-    if (output == stdout) {
-	fprintf(stdout, "/**INDENT** %s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stdout, "%s", msg);
-	fprintf(stdout, " */\n");
-    }
-    else {
-	fprintf(stderr, "%s@%d: ", level == 0 ? "Warning" : "Error", line_no);
-	fprintf(stderr, "%s", msg);
-	fprintf(stderr, "\n");
-    }
-}
-