diff --git a/contrib/cube/cubescan.l b/contrib/cube/cubescan.l
index 289d23120dd..9d2b4ae18cb 100644
--- a/contrib/cube/cubescan.l
+++ b/contrib/cube/cubescan.l
@@ -9,6 +9,7 @@
 #define YY_READ_BUF_SIZE 16777216
 
 /* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
 #define fprintf(file, fmt, msg)  ereport(ERROR, (errmsg_internal("%s", msg)))
 
 /* Handles to the buffer that the lexer uses internally */
diff --git a/contrib/seg/segscan.l b/contrib/seg/segscan.l
index 24ad662910f..817300993dd 100644
--- a/contrib/seg/segscan.l
+++ b/contrib/seg/segscan.l
@@ -9,6 +9,7 @@
 #define YY_READ_BUF_SIZE 16777216
 
 /* Avoid exit() on fatal scanner errors (a bit ugly -- see yy_fatal_error) */
+#undef fprintf
 #define fprintf(file, fmt, msg)  ereport(ERROR, (errmsg_internal("%s", msg)))
 
 /* Handles to the buffer that the lexer uses internally */
diff --git a/contrib/tsearch2/wordparser/parser.l b/contrib/tsearch2/wordparser/parser.l
index 179c99c9dac..a7cb4684c32 100644
--- a/contrib/tsearch2/wordparser/parser.l
+++ b/contrib/tsearch2/wordparser/parser.l
@@ -6,6 +6,7 @@
 #include "common.h"
 
 /* Avoid exit() on fatal scanner errors */
+#undef fprintf
 #define fprintf(file, fmt, msg)  ts_error(ERROR, fmt, msg)
 
 char *token = NULL;  /* pointer to token */