diff --git a/src/style-spec/function/index.js b/src/style-spec/function/index.js
index e3c5db5ea9c..0f304ebd5ef 100644
--- a/src/style-spec/function/index.js
+++ b/src/style-spec/function/index.js
@@ -292,7 +292,9 @@ function interpolationFactor(input, base, lowerValue, upperValue) {
     const difference = upperValue - lowerValue;
     const progress = input - lowerValue;
 
-    if (base === 1) {
+    if (difference === 0) {
+        return 0;
+    } else if (base === 1) {
         return progress / difference;
     } else {
         return (Math.pow(base, progress) - 1) / (Math.pow(base, difference) - 1);
diff --git a/test/unit/style-spec/function.test.js b/test/unit/style-spec/function.test.js
index 0248082e23c..16ad4a64b1c 100644
--- a/test/unit/style-spec/function.test.js
+++ b/test/unit/style-spec/function.test.js
@@ -56,9 +56,9 @@ test('binary search', (t) => {
             type: 'number',
             function: 'interpolated'
         });
-        // Nan because the interpolation will fail when given to stops with the same value.
-        // This is however more desirable than looping forever.
-        t.equal(isNaN(f(17)), true);
+
+        t.equal(f(17), 11);
+
         t.end();
     });
     t.end();