diff --git a/src/com/android/settings/widget/DonutView.java b/src/com/android/settings/widget/DonutView.java
index 4fb3c5b2464..c5ac40bde79 100644
--- a/src/com/android/settings/widget/DonutView.java
+++ b/src/com/android/settings/widget/DonutView.java
@@ -37,6 +37,7 @@ import android.text.style.RelativeSizeSpan;
 import android.util.AttributeSet;
 import android.view.View;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.settings.R;
 import com.android.settings.Utils;
 
@@ -173,19 +174,13 @@ public class DonutView extends View {
         final float centerY = getHeight() / 2;
         final float totalHeight = getTextHeight(mTextPaint) + getTextHeight(mBigNumberPaint);
         final float startY = centerY + totalHeight / 2;
-        final float fontProportion = getResources().getDimension(
-                R.dimen.storage_donut_view_percent_sign_size) /
-                getResources().getDimension(R.dimen.storage_donut_view_percent_text_size);
         // Support from Android P
         final String localizedPercentSign = new DecimalFormatSymbols().getPercentString();
-        final int startIndex = mPercentString.indexOf(localizedPercentSign);
-        final int endIndex = startIndex + localizedPercentSign.length();
 
         // The first line y-coordinates start at (total height - all TextPaint height) / 2
         canvas.save();
-        final Spannable percentStringSpan = new SpannableString(mPercentString);
-        percentStringSpan.setSpan(new RelativeSizeSpan(fontProportion),
-                startIndex, endIndex, Spanned.SPAN_INCLUSIVE_INCLUSIVE);
+        final Spannable percentStringSpan =
+                getPercentageStringSpannable(getResources(), mPercentString, localizedPercentSign);
         final StaticLayout percentStringLayout = new StaticLayout(percentStringSpan,
                 mBigNumberPaint, getWidth(), Layout.Alignment.ALIGN_CENTER, 1, 0, false);
         canvas.translate(0, (getHeight() - totalHeight) / 2);
@@ -235,6 +230,30 @@ public class DonutView extends View {
         invalidate();
     }
 
+    @VisibleForTesting
+    static Spannable getPercentageStringSpannable(
+            Resources resources, String percentString, String percentageSignString) {
+        final float fontProportion =
+                resources.getDimension(R.dimen.storage_donut_view_percent_sign_size)
+                        / resources.getDimension(R.dimen.storage_donut_view_percent_text_size);
+        final Spannable percentStringSpan = new SpannableString(percentString);
+        int startIndex = percentString.indexOf(percentageSignString);
+        int endIndex = startIndex + percentageSignString.length();
+
+        // Fallback to no small string if we can't find the percentage sign.
+        if (startIndex < 0) {
+            startIndex = 0;
+            endIndex = percentString.length();
+        }
+
+        percentStringSpan.setSpan(
+                new RelativeSizeSpan(fontProportion),
+                startIndex,
+                endIndex,
+                Spanned.SPAN_EXCLUSIVE_INCLUSIVE);
+        return percentStringSpan;
+    }
+
     private float getTextHeight(TextPaint paint) {
         // Technically, this should be the cap height, but I can live with the descent - ascent.
         return paint.descent() - paint.ascent();
diff --git a/tests/robotests/src/com/android/settings/widget/DonutViewTest.java b/tests/robotests/src/com/android/settings/widget/DonutViewTest.java
new file mode 100644
index 00000000000..3b8bdceeb93
--- /dev/null
+++ b/tests/robotests/src/com/android/settings/widget/DonutViewTest.java
@@ -0,0 +1,19 @@
+package com.android.settings.widget;
+
+import android.content.Context;
+
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class DonutViewTest {
+    @Test
+    public void getPercentageStringSpannable_doesntCrashForMissingPercentage() {
+        Context context = RuntimeEnvironment.application;
+
+        DonutView.getPercentageStringSpannable(context.getResources(), "50%", "h");
+    }
+}