diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2a3232a..70826293 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@
 - _...Add new stuff here..._
 
 ### 🐞 Bug fixes
+- Prevent a crash when converting a function to an expression
+- Prevent a crash when deleting either stop from a function with two stops
 - Preserve expanded layer groups when deleting layers, including the first layer of a group
 - The map's data listener now fires on tile loads again, so source and vector layer field autocompletion is populated
 - The `maputnik` desktop binary now opens the default browser automatically on startup (opt out with `--no-browser`)
diff --git a/e2e/layer-editor.spec.ts b/e2e/layer-editor.spec.ts
index 4c2c49ce..8b35ef9d 100644
--- a/e2e/layer-editor.spec.ts
+++ b/e2e/layer-editor.spec.ts
@@ -289,6 +289,20 @@ describe("layer editor", () => {
         });
       });
 
+      test("should leave a plain editable value after deleting a stop", async () => {
+        await when.setFunctionStopValue("circle-radius", "Output value", 1, "0");
+        await when.deleteFunctionStop("circle-radius");
+        await then(get.elementByTestId("spec-field:circle-radius")).shouldBeVisible();
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": 0 } }],
+        });
+
+        await when.setValue("spec-field-input:circle-radius", "7");
+        await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
+          layers: [{ id, paint: { "circle-radius": 7 } }],
+        });
+      });
+
       test("should set the base", async () => {
         await when.setFunctionBase("circle-radius", "2");
         await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
@@ -310,8 +324,9 @@ describe("layer editor", () => {
         });
       });
 
-      test("should convert to an expression", async () => {
+      test("should convert to an expression without crashing", async () => {
         await when.makeExpression("circle-radius");
+        await then(get.element("[data-wd-key='spec-field-container:circle-radius'] .maputnik-expression-editor")).shouldBeVisible();
         await then(get.styleFromLocalStorage()).shouldDeepNestedInclude({
           layers: [{ id, paint: { "circle-radius": ["interpolate", ["linear"], ["zoom"], 6, 5, 10, 5] } }],
         });
diff --git a/src/components/FieldFunction.tsx b/src/components/FieldFunction.tsx
index eb995477..3a761520 100644
--- a/src/components/FieldFunction.tsx
+++ b/src/components/FieldFunction.tsx
@@ -129,16 +129,10 @@ type FieldFunctionProps = {
  * https://www.mapbox.com/mapbox-gl-style-spec/#types-function-zoom-property
  */
 export const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
-  const [dataType, setDataType] = React.useState(
-    getDataType(props.value, props.fieldSpec)
-  );
   const [isEditing, setIsEditing] = React.useState(false);
-
-  React.useEffect(() => {
-    if (!isEditing) {
-      setDataType(getDataType(props.value, props.fieldSpec));
-    }
-  }, [props.value, props.fieldSpec, isEditing]);
+  // Keep the expression editor mounted while typing, but otherwise select the
+  // editor from the current value so a collapsed function never renders as stops.
+  const dataType = isEditing ? "expression" : getDataType(props.value, props.fieldSpec);
 
   const getFieldFunctionType = (fieldSpec: any) => {
     if (fieldSpec.expression.interpolated) {
@@ -173,7 +167,7 @@ export const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
   const deleteExpression = () => {
     const { fieldSpec, fieldName } = props;
     props.onChange(fieldName, fieldSpec.default);
-    setDataType("value");
+    setIsEditing(false);
   };
 
   const deleteStop = (stopIdx: number) => {
@@ -233,10 +227,10 @@ export const FieldFunction: React.FC<FieldFunctionProps> = (props) => {
         type: "identity",
         property: value[1],
       });
-      setDataType("value");
+      setIsEditing(false);
     } else if (isLiteralExpression(value)) {
       props.onChange(fieldName, value[1]);
-      setDataType("value");
+      setIsEditing(false);
     }
   };