diff --git a/src/lib/coerce.js b/src/lib/coerce.js
index 667fdbf0dc1..eacdfe1f637 100644
--- a/src/lib/coerce.js
+++ b/src/lib/coerce.js
@@ -44,6 +44,20 @@ exports.valObjects = {
             if(opts.coerceNumber) v = +v;
             if(opts.values.indexOf(v) === -1) propOut.set(dflt);
             else propOut.set(v);
+        },
+        validateFunction: function(v, opts) {
+            if(opts.coerceNumber) v = +v;
+
+            var values = opts.values;
+            for(var i = 0; i < values.length; i++) {
+                var k = String(values[i]);
+
+                if((k.charAt(0) === '/' && k.charAt(k.length - 1) === '/')) {
+                    var regex = new RegExp(k.substr(1, k.length - 2));
+                    if(regex.test(v)) return true;
+                } else if(v === values[i]) return true;
+            }
+            return false;
         }
     },
     'boolean': {
diff --git a/src/plot_api/validate.js b/src/plot_api/validate.js
index 40e9977f448..91c0dc5d15d 100644
--- a/src/plot_api/validate.js
+++ b/src/plot_api/validate.js
@@ -219,6 +219,11 @@ function crawl(objIn, objOut, schema, list, base, path) {
         else if(!Lib.validate(valIn, nestedSchema)) {
             list.push(format('value', base, p, valIn));
         }
+        else if(nestedSchema.valType === 'enumerated' &&
+            ((nestedSchema.coerceNumber && valIn !== +valOut) || valIn !== valOut)
+        ) {
+            list.push(format('dynamic', base, p, valIn, valOut));
+        }
     }
 
     return list;
@@ -267,6 +272,16 @@ var code2msgFunc = {
 
         return inBase(base) + target + ' ' + astr + ' did not get coerced';
     },
+    dynamic: function(base, astr, valIn, valOut) {
+        return [
+            inBase(base) + 'key',
+            astr,
+            '(set to \'' + valIn + '\')',
+            'got reset to',
+            '\'' + valOut + '\'',
+            'during defaults.'
+        ].join(' ');
+    },
     invisible: function(base) {
         return 'Trace ' + base[1] + ' got defaulted to be not visible';
     },
@@ -284,7 +299,7 @@ function inBase(base) {
     return 'In ' + base + ', ';
 }
 
-function format(code, base, path, valIn) {
+function format(code, base, path, valIn, valOut) {
     path = path || '';
 
     var container, trace;
@@ -301,8 +316,8 @@ function format(code, base, path, valIn) {
         trace = null;
     }
 
-    var astr = convertPathToAttributeString(path),
-        msg = code2msgFunc[code](base, astr, valIn);
+    var astr = convertPathToAttributeString(path);
+    var msg = code2msgFunc[code](base, astr, valIn, valOut);
 
     // log to console if logger config option is enabled
     Lib.log(msg);
diff --git a/test/jasmine/tests/lib_test.js b/test/jasmine/tests/lib_test.js
index edd5abfdf71..69573e1aa85 100644
--- a/test/jasmine/tests/lib_test.js
+++ b/test/jasmine/tests/lib_test.js
@@ -978,6 +978,12 @@ describe('Test lib.js:', function() {
                 arrayOk: true,
                 dflt: 'a'
             });
+
+            assert(['x', 'x2'], ['xx', 'x0', undefined], {
+                valType: 'enumerated',
+                values: ['/^x([2-9]|[1-9][0-9]+)?$/'],
+                dflt: 'x'
+            });
         });
 
         it('should work for valType \'boolean\' where', function() {
diff --git a/test/jasmine/tests/validate_test.js b/test/jasmine/tests/validate_test.js
index b95061938db..d5597f23322 100644
--- a/test/jasmine/tests/validate_test.js
+++ b/test/jasmine/tests/validate_test.js
@@ -392,4 +392,45 @@ describe('Plotly.validate', function() {
             'In data trace 2, key transforms[0].type is set to an invalid value (no gonna work)'
         );
     });
+
+    it('should catch input errors for attribute with dynamic defaults', function() {
+        var out = Plotly.validate([], {
+            xaxis: {
+                constrain: 'domain',
+                constraintoward: 'bottom'
+            },
+            yaxis: {
+                constrain: 'domain',
+                constraintoward: 'left'
+            },
+            xaxis2: {
+                anchor: 'x3'
+            },
+            yaxis2: {
+                overlaying: 'x'
+            }
+        });
+
+        expect(out.length).toBe(4);
+        assertErrorContent(
+            out[0], 'dynamic', 'layout', null,
+            ['xaxis', 'constraintoward'], 'xaxis.constraintoward',
+            'In layout, key xaxis.constraintoward (set to \'bottom\') got reset to \'center\' during defaults.'
+        );
+        assertErrorContent(
+            out[1], 'dynamic', 'layout', null,
+            ['yaxis', 'constraintoward'], 'yaxis.constraintoward',
+            'In layout, key yaxis.constraintoward (set to \'left\') got reset to \'middle\' during defaults.'
+        );
+        assertErrorContent(
+            out[2], 'dynamic', 'layout', null,
+            ['xaxis2', 'anchor'], 'xaxis2.anchor',
+            'In layout, key xaxis2.anchor (set to \'x3\') got reset to \'y\' during defaults.'
+        );
+        assertErrorContent(
+            out[3], 'dynamic', 'layout', null,
+            ['yaxis2', 'overlaying'], 'yaxis2.overlaying',
+            'In layout, key yaxis2.overlaying (set to \'x\') got reset to \'false\' during defaults.'
+        );
+    });
 });