diff --git a/addons/web/static/src/views/form/form_compiler.js b/addons/web/static/src/views/form/form_compiler.js
index 4c5ceb5c630..d06acb5a23b 100644
--- a/addons/web/static/src/views/form/form_compiler.js
+++ b/addons/web/static/src/views/form/form_compiler.js
@@ -144,11 +144,10 @@ export class FormCompiler extends ViewCompiler {
                         ? `!evalDomainFromRecord(props.record,${JSON.stringify(invisible)})`
                         : true,
             });
-            const button = this.compileNode(child, params, false);
-            if (button.tagName === "ViewButton") {
-                button.setAttribute("defaultRank", "'oe_stat_button'");
+            if (child.tagName === "button") {
+                child.classList.add("oe_stat_button");
             }
-            append(mainSlot, button);
+            append(mainSlot, this.compileNode(child, params, false));
             append(buttonBox, mainSlot);
         }
 
@@ -364,6 +363,9 @@ export class FormCompiler extends ViewCompiler {
                 compiled.setAttribute("showTooltip", true);
                 others.push(compiled);
             } else {
+                if (compiled.tagName === "ViewButton") {
+                    compiled.setAttribute("defaultRank", "'btn-secondary'");
+                }
                 buttons.push(compiled);
             }
         }
diff --git a/addons/web/static/src/views/view_button/view_button.js b/addons/web/static/src/views/view_button/view_button.js
index c0649514aef..2c31d2354a4 100644
--- a/addons/web/static/src/views/view_button/view_button.js
+++ b/addons/web/static/src/views/view_button/view_button.js
@@ -90,18 +90,21 @@ export class ViewButton extends Component {
     getClassName() {
         const classNames = [];
         let hasExplicitRank = false;
-        for (let cls of this.props.className.split(" ")) {
-            if (cls in odooToBootstrapClasses) {
-                cls = odooToBootstrapClasses[cls];
-            }
-            classNames.push(cls);
-            if (!hasExplicitRank && explicitRankClasses.includes(cls)) {
-                hasExplicitRank = true;
+        if (this.props.className) {
+            for (let cls of this.props.className.split(" ")) {
+                if (cls in odooToBootstrapClasses) {
+                    cls = odooToBootstrapClasses[cls];
+                }
+                classNames.push(cls);
+                if (!hasExplicitRank && explicitRankClasses.includes(cls)) {
+                    hasExplicitRank = true;
+                }
             }
         }
         if (this.props.tag === "button") {
-            classNames.push("btn");
-            if (!hasExplicitRank) {
+            const hasOtherClasses = classNames.length;
+            classNames.unshift("btn");
+            if ((!hasExplicitRank && this.props.defaultRank) || !hasOtherClasses) {
                 classNames.push(this.props.defaultRank || "btn-secondary");
             }
             if (this.props.size) {
diff --git a/addons/web/static/tests/views/form/form_view_tests.js b/addons/web/static/tests/views/form/form_view_tests.js
index de87d623b91..15971e11eee 100644
--- a/addons/web/static/tests/views/form/form_view_tests.js
+++ b/addons/web/static/tests/views/form/form_view_tests.js
@@ -2482,25 +2482,31 @@ QUnit.module("Views", (hooks) => {
             resId: 2,
         });
 
-        assert.hasClass(target.querySelector('button[name="0"]'), "btn btn-secondary");
-        assert.hasClass(target.querySelector('button[name="1"]'), "btn btn-primary");
-        assert.hasClass(target.querySelector('button[name="2"]'), "btn btn-primary");
-        assert.hasClass(target.querySelector('button[name="3"]'), "btn btn-secondary");
-        assert.hasClass(target.querySelector('button[name="4"]'), "btn btn-link");
-        assert.hasClass(target.querySelector('button[name="5"]'), "btn btn-link");
-        assert.hasClass(target.querySelector('button[name="6"]'), "btn btn-success");
-        assert.hasClass(
-            target.querySelector('button[name="7"]'),
+        assert.strictEqual(target.querySelector('button[name="0"]').className, "btn btn-secondary");
+        assert.strictEqual(target.querySelector('button[name="1"]').className, "btn btn-primary");
+        assert.strictEqual(target.querySelector('button[name="2"]').className, "btn btn-primary");
+        assert.strictEqual(target.querySelector('button[name="3"]').className, "btn btn-secondary");
+        assert.strictEqual(target.querySelector('button[name="4"]').className, "btn btn-link");
+        assert.strictEqual(target.querySelector('button[name="5"]').className, "btn btn-link");
+        assert.strictEqual(target.querySelector('button[name="6"]').className, "btn btn-success");
+        assert.strictEqual(
+            target.querySelector('button[name="7"]').className,
             "btn o_this_is_a_button btn-secondary"
         );
-        assert.hasClass(target.querySelector('button[name="8"]'), "btn btn-secondary");
-        assert.hasClass(target.querySelector('button[name="9"]'), "btn btn-primary");
-        assert.hasClass(target.querySelector('button[name="10"]'), "btn btn-primary");
-        assert.hasClass(target.querySelector('button[name="11"]'), "btn btn-secondary");
-        assert.hasClass(target.querySelector('button[name="12"]'), "btn btn-link");
-        assert.hasClass(target.querySelector('button[name="13"]'), "btn btn-link");
-        assert.hasClass(target.querySelector('button[name="14"]'), "btn btn-success");
-        assert.hasClass(target.querySelector('button[name="15"]'), "btn o_this_is_a_button");
+        assert.strictEqual(target.querySelector('button[name="8"]').className, "btn btn-secondary");
+        assert.strictEqual(target.querySelector('button[name="9"]').className, "btn btn-primary");
+        assert.strictEqual(target.querySelector('button[name="10"]').className, "btn btn-primary");
+        assert.strictEqual(
+            target.querySelector('button[name="11"]').className,
+            "btn btn-secondary"
+        );
+        assert.strictEqual(target.querySelector('button[name="12"]').className, "btn btn-link");
+        assert.strictEqual(target.querySelector('button[name="13"]').className, "btn btn-link");
+        assert.strictEqual(target.querySelector('button[name="14"]').className, "btn btn-success");
+        assert.strictEqual(
+            target.querySelector('button[name="15"]').className,
+            "btn o_this_is_a_button"
+        );
     });
 
     QUnit.test("button in form view and long willStart", async function (assert) {