diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c
index 67e1c59951a..0d755c69b2d 100644
--- a/contrib/postgres_fdw/option.c
+++ b/contrib/postgres_fdw/option.c
@@ -116,15 +116,18 @@ postgres_fdw_validator(PG_FUNCTION_ARGS)
 		else if (strcmp(def->defname, "fdw_startup_cost") == 0 ||
 				 strcmp(def->defname, "fdw_tuple_cost") == 0)
 		{
-			/* these must have a non-negative numeric value */
+			/*
+			 * These must have a floating point value greater than or equal to
+			 * zero.
+			 */
 			double		val;
 			char	   *endp;
 
 			val = strtod(defGetString(def), &endp);
 			if (*endp || val < 0)
 				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("%s requires a non-negative numeric value",
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("\"%s\" must be a floating point value greater than or equal to zero",
 								def->defname)));
 		}
 		else if (strcmp(def->defname, "extensions") == 0)
@@ -139,8 +142,8 @@ postgres_fdw_validator(PG_FUNCTION_ARGS)
 			fetch_size = strtol(defGetString(def), NULL, 10);
 			if (fetch_size <= 0)
 				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("%s requires a non-negative integer value",
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("\"%s\" must be an integer value greater than zero",
 								def->defname)));
 		}
 	}
diff --git a/doc/src/sgml/sources.sgml b/doc/src/sgml/sources.sgml
index a1a14a43a07..179f4a19c2c 100644
--- a/doc/src/sgml/sources.sgml
+++ b/doc/src/sgml/sources.sgml
@@ -806,6 +806,16 @@ BETTER: unrecognized node type: 42
    </para>
   </formalpara>
 
+  <formalpara>
+    <title>Non-negative</title>
+   <para>
+    Avoid <quote>non-negative</quote> as it is ambiguous
+    about whether it accepts zero.  It's better to use
+    <quote>greater than zero</quote> or
+    <quote>greater than or equal to zero</quote>.
+   </para>
+  </formalpara>
+
   </simplesect>
 
   <simplesect>
diff --git a/src/backend/utils/adt/tsquery_op.c b/src/backend/utils/adt/tsquery_op.c
index 755c3e9ee8e..f575afe299a 100644
--- a/src/backend/utils/adt/tsquery_op.c
+++ b/src/backend/utils/adt/tsquery_op.c
@@ -120,7 +120,7 @@ tsquery_phrase_distance(PG_FUNCTION_ARGS)
 	if (distance < 0 || distance > MAXENTRYPOS)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("distance in phrase operator should be non-negative and less than %d",
+				 errmsg("distance in phrase operator must be an integer value between zero and %d inclusive",
 						MAXENTRYPOS)));
 	if (a->size == 0)
 	{
diff --git a/src/test/modules/test_shm_mq/test.c b/src/test/modules/test_shm_mq/test.c
index 7a6ad23f755..0a6290f9b45 100644
--- a/src/test/modules/test_shm_mq/test.c
+++ b/src/test/modules/test_shm_mq/test.c
@@ -57,17 +57,17 @@ test_shm_mq(PG_FUNCTION_ARGS)
 	if (loop_count < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("repeat count size must be a non-negative integer")));
+				 errmsg("repeat count size must be an integer value greater than or equal to zero")));
 
 	/*
 	 * Since this test sends data using the blocking interfaces, it cannot
 	 * send data to itself.  Therefore, a minimum of 1 worker is required. Of
 	 * course, a negative worker count is nonsensical.
 	 */
-	if (nworkers < 1)
+	if (nworkers <= 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("number of workers must be a positive integer")));
+				 errmsg("number of workers must be an integer value greater than zero")));
 
 	/* Set up dynamic shared memory segment and background workers. */
 	test_shm_mq_setup(queue_size, nworkers, &seg, &outqh, &inqh);
@@ -149,7 +149,7 @@ test_shm_mq_pipelined(PG_FUNCTION_ARGS)
 	if (loop_count < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("repeat count size must be a non-negative integer")));
+				 errmsg("repeat count size must be an integer value greater than or equal to zero")));
 
 	/*
 	 * Using the nonblocking interfaces, we can even send data to ourselves,
@@ -158,7 +158,7 @@ test_shm_mq_pipelined(PG_FUNCTION_ARGS)
 	if (nworkers < 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("number of workers must be a non-negative integer")));
+				 errmsg("number of workers must be an integer value greater than or equal to zero")));
 
 	/* Set up dynamic shared memory segment and background workers. */
 	test_shm_mq_setup(queue_size, nworkers, &seg, &outqh, &inqh);