diff --git a/adminer/static/functions.js b/adminer/static/functions.js
index ce2dddbf..c34b1cf9 100644
--- a/adminer/static/functions.js
+++ b/adminer/static/functions.js
@@ -540,20 +540,22 @@ function editingKeydown(event) {
 */
 function functionChange() {
 	var input = this.form[this.name.replace(/^function/, 'fields')];
-	if (selectValue(this)) {
-		if (input.origType === undefined) {
-			input.origType = input.type;
-			input.origMaxLength = input.getAttribute('data-maxlength');
-		}
-		input.removeAttribute('data-maxlength');
-		input.type = 'text';
-	} else if (input.origType) {
-		input.type = input.origType;
-		if (input.origMaxLength >= 0) {
-			input.setAttribute('data-maxlength', input.origMaxLength);
+	if (input) { // undefined with the set data type
+		if (selectValue(this)) {
+			if (input.origType === undefined) {
+				input.origType = input.type;
+				input.origMaxLength = input.getAttribute('data-maxlength');
+			}
+			input.removeAttribute('data-maxlength');
+			input.type = 'text';
+		} else if (input.origType) {
+			input.type = input.origType;
+			if (input.origMaxLength >= 0) {
+				input.setAttribute('data-maxlength', input.origMaxLength);
+			}
 		}
+		oninput({target: input});
 	}
-	oninput({target: input});
 	helpClose();
 }
 
diff --git a/changes.txt b/changes.txt
index 38fd81eb..baa2a887 100644
--- a/changes.txt
+++ b/changes.txt
@@ -1,6 +1,7 @@
 Adminer 4.6.4-dev:
 Fix inline editing of empty cells (regression from 4.6.3)
 Allow adding more than two indexes and forign key columns at a time (regression from 4.4.0)
+Fix function change with set data type
 
 Adminer 4.6.3 (released 2018-06-28):
 Disallow using password-less databases