diff --git a/src/lib/coerce.js b/src/lib/coerce.js
index b974f323016..51c810b34b4 100644
--- a/src/lib/coerce.js
+++ b/src/lib/coerce.js
@@ -322,7 +322,7 @@ exports.coerce2 = function(containerIn, containerOut, attributes, attribute, dfl
     var propIn = nestedProperty(containerIn, attribute),
         propOut = exports.coerce(containerIn, containerOut, attributes, attribute, dflt);
 
-    return propIn.get() ? propOut : false;
+    return propIn.get() !== undefined ? propOut : false;
 };
 
 /*
diff --git a/src/traces/contour/defaults.js b/src/traces/contour/defaults.js
index e88b43cbe7f..e9253b42066 100644
--- a/src/traces/contour/defaults.js
+++ b/src/traces/contour/defaults.js
@@ -33,7 +33,7 @@ module.exports = function supplyDefaults(traceIn, traceOut, defaultColor, layout
 
     var contourStart = Lib.coerce2(traceIn, traceOut, attributes, 'contours.start'),
         contourEnd = Lib.coerce2(traceIn, traceOut, attributes, 'contours.end'),
-        autocontour = coerce('autocontour', !(contourStart && contourEnd));
+        autocontour = coerce('autocontour', contourStart === false || contourEnd === false);
 
     if(autocontour) coerce('ncontours');
     else coerce('contours.size');