diff --git a/public/app/plugins/datasource/prometheus/querybuilder/shared/AutoSizeInput.tsx b/public/app/plugins/datasource/prometheus/querybuilder/shared/AutoSizeInput.tsx
index b5d242a20a1..f3904dcc272 100644
--- a/public/app/plugins/datasource/prometheus/querybuilder/shared/AutoSizeInput.tsx
+++ b/public/app/plugins/datasource/prometheus/querybuilder/shared/AutoSizeInput.tsx
@@ -11,9 +11,9 @@ export interface Props extends InputProps {
 }
 
 export const AutoSizeInput = React.forwardRef<HTMLInputElement, Props>((props, ref) => {
-  const { defaultValue, minWidth = 10, maxWidth, onCommitChange, onKeyDown, onBlur, ...restProps } = props;
-  const [value, setValue] = React.useState('');
-  const [inputWidth, setInputWidth] = React.useState(0);
+  const { defaultValue = '', minWidth = 10, maxWidth, onCommitChange, onKeyDown, onBlur, ...restProps } = props;
+  const [value, setValue] = React.useState(defaultValue.toString());
+  const [inputWidth, setInputWidth] = React.useState(minWidth);
 
   useEffect(() => {
     setInputWidth(getWidthFor(value.toString(), minWidth, maxWidth));
@@ -21,9 +21,7 @@ export const AutoSizeInput = React.forwardRef<HTMLInputElement, Props>((props, r
 
   useEffect(() => {
     setInputWidth(minWidth);
-    if (defaultValue) {
-      setValue(defaultValue.toString());
-    }
+    setValue(defaultValue.toString());
   }, [minWidth, defaultValue]);
 
   return (