diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index bc6e2a6..0010572 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -57,66 +57,66 @@
 
 /* Read an integer field (anything written as ":fldname %d") */
 #define READ_INT_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = atoi(token)
 
 /* Read an unsigned integer field (anything written as ":fldname %u") */
 #define READ_UINT_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = atoui(token)
 
 /* Read an OID field (don't hard-wire assumption that OID is same as uint) */
 #define READ_OID_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = atooid(token)
 
 /* Read a char field (ie, one ascii character) */
 #define READ_CHAR_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = token[0]
 
 /* Read an enumerated-type field that was written as an integer code */
 #define READ_ENUM_FIELD(fldname, enumtype) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = (enumtype) atoi(token)
 
 /* Read a float field */
 #define READ_FLOAT_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = atof(token)
 
 /* Read a boolean field */
 #define READ_BOOL_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = strtobool(token)
 
 /* Read a character-string field */
 #define READ_STRING_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = nullable_string(token, length)
 
 /* Read a parse location field (and throw away the value, per notes above) */
 #define READ_LOCATION_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
-	token = pg_strtok(&length);		/* get field value */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* get field value */ \
 	local_node->fldname = -1	/* set field to "unknown" */
 
 /* Read a Node field */
 #define READ_NODE_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
 	local_node->fldname = nodeRead(NULL, 0)
 
 /* Read a bitmapset field */
 #define READ_BITMAPSET_FIELD(fldname) \
-	token = pg_strtok(&length);		/* skip :fldname */ \
+	token = pg_strtok_mandatory(&length);		/* skip :fldname */ \
 	local_node->fldname = _readBitmapset()
 
 /* Routine exit */
@@ -139,8 +139,20 @@
 #define nullable_string(token,length)  \
 	((length) == 0 ? NULL : debackslash(token, length))
 
-
 static Datum readDatum(bool typbyval);
+static char *pg_strtok_mandatory(int *length);
+
+/*
+ * Like pg_strtok(), but throws an error on end of string
+ */
+static char *
+pg_strtok_mandatory(int *length)
+{
+	char *token = pg_strtok(length);
+	if (token == NULL)
+		elog(ERROR, "unexpected end of string while reading tree node");
+	return token;
+}
 
 /*
  * _readBitmapset
@@ -427,9 +439,9 @@ _readConst(void)
 	READ_BOOL_FIELD(constisnull);
 	READ_LOCATION_FIELD(location);
 
-	token = pg_strtok(&length); /* skip :constvalue */
+	token = pg_strtok_mandatory(&length); /* skip :constvalue */
 	if (local_node->constisnull)
-		token = pg_strtok(&length);		/* skip "<>" */
+		token = pg_strtok_mandatory(&length);		/* skip "<>" */
 	else
 		local_node->constvalue = readDatum(local_node->constbyval);
 
@@ -640,8 +652,8 @@ _readBoolExpr(void)
 	READ_LOCALS(BoolExpr);
 
 	/* do-it-yourself enum representation */
-	token = pg_strtok(&length); /* skip :boolop */
-	token = pg_strtok(&length); /* get field value */
+	token = pg_strtok_mandatory(&length); /* skip :boolop */
+	token = pg_strtok_mandatory(&length); /* get field value */
 	if (strncmp(token, "and", 3) == 0)
 		local_node->boolop = AND_EXPR;
 	else if (strncmp(token, "or", 2) == 0)
@@ -1182,7 +1194,7 @@ _readRangeTblEntry(void)
  * Given a character string representing a node tree, parseNodeString creates
  * the internal node structure.
  *
- * The string to be read must already have been loaded into pg_strtok().
+ * The string to be read must already have been loaded into pg_strtok_mandatory().
  */
 Node *
 parseNodeString(void)
@@ -1191,7 +1203,7 @@ parseNodeString(void)
 
 	READ_TEMP_LOCALS();
 
-	token = pg_strtok(&length);
+	token = pg_strtok_mandatory(&length);
 
 #define MATCH(tokname, namelen) \
 	(length == namelen && strncmp(token, tokname, namelen) == 0)
@@ -1328,7 +1340,7 @@ readDatum(bool typbyval)
 	/*
 	 * read the actual length of the value
 	 */
-	token = pg_strtok(&tokenLength);
+	token = pg_strtok_mandatory(&tokenLength);
 	length = atoui(token);
 
 	token = pg_strtok(&tokenLength);	/* read the '[' */
@@ -1346,7 +1358,7 @@ readDatum(bool typbyval)
 		s = (char *) (&res);
 		for (i = 0; i < (Size) sizeof(Datum); i++)
 		{
-			token = pg_strtok(&tokenLength);
+			token = pg_strtok_mandatory(&tokenLength);
 			s[i] = (char) atoi(token);
 		}
 	}
@@ -1357,7 +1369,7 @@ readDatum(bool typbyval)
 		s = (char *) palloc(length);
 		for (i = 0; i < length; i++)
 		{
-			token = pg_strtok(&tokenLength);
+			token = pg_strtok_mandatory(&tokenLength);
 			s[i] = (char) atoi(token);
 		}
 		res = PointerGetDatum(s);