diff --git a/draftlogs/8125_fix.md b/draftlogs/8125_fix.md
new file mode 100644
index 00000000000..ed4aa06379b
--- /dev/null
+++ b/draftlogs/8125_fix.md
@@ -0,0 +1 @@
+ - Fix normalization of `contours.value` for interval constraints in `contour` and `contourcarpet` [[#8125](https://github.com/plotly/plotly.js/pull/8125)]
diff --git a/src/traces/contour/constraint_defaults.js b/src/traces/contour/constraint_defaults.js
index 2b0178d940f..280bef22dd6 100644
--- a/src/traces/contour/constraint_defaults.js
+++ b/src/traces/contour/constraint_defaults.js
@@ -57,10 +57,10 @@ function handleConstraintValueDefaults(coerce, contours) {
                 contours.value = [zvalue, zvalue + 1];
             }
         } else if(contours.value.length > 2) {
-            contours.value = contours.value.slice(2);
-        } else if(contours.length === 0) {
+            contours.value = contours.value.slice(0, 2);
+        } else if(contours.value.length === 0) {
             contours.value = [0, 1];
-        } else if(contours.length < 2) {
+        } else if(contours.value.length < 2) {
             zvalue = parseFloat(contours.value[0]);
             contours.value = [zvalue, zvalue + 1];
         } else {
diff --git a/test/jasmine/tests/contour_test.js b/test/jasmine/tests/contour_test.js
index ae098a30702..5a842fce097 100644
--- a/test/jasmine/tests/contour_test.js
+++ b/test/jasmine/tests/contour_test.js
@@ -115,6 +115,45 @@ describe('contour defaults', function() {
         expect(traceOut.xcalendar).toBe('coptic');
         expect(traceOut.ycalendar).toBe('ethiopian');
     });
+
+    it('should coerce constraint interval values to two numbers', function() {
+        var specs = [
+            {
+                value: [],
+                expected: [0, 1]
+            },
+            {
+                value: [5],
+                expected: [5, 6]
+            },
+            {
+                value: [10, 20],
+                expected: [10, 20]
+            },
+            {
+                value: [10, 20, 30],
+                expected: [10, 20]
+            }
+        ];
+    
+        specs.forEach(function(spec) {
+            traceIn = {
+                type: 'contour',
+                z: [[0, 1], [2, 3]],
+                contours: {
+                    type: 'constraint',
+                    operation: '[]',
+                    value: spec.value
+                }
+            };
+    
+            traceOut = {};
+    
+            supplyDefaults(traceIn, traceOut, defaultColor, layout);
+    
+            expect(traceOut.contours.value).toEqual(spec.expected);
+        });
+    });
 });
 
 describe('contour makeColorMap', function() {