diff --git a/packages/mui-material/src/FilledInput/FilledInput.js b/packages/mui-material/src/FilledInput/FilledInput.js
index 99200acd1c8579..fd450188ce4dfb 100644
--- a/packages/mui-material/src/FilledInput/FilledInput.js
+++ b/packages/mui-material/src/FilledInput/FilledInput.js
@@ -95,9 +95,6 @@ const FilledInputRoot = styled(InputBaseRoot, {
         '&:before, &:after': {
           borderBottomColor: (theme.vars || theme).palette.error.main,
         },
-        '&:focus-within:after': {
-          transform: 'scaleX(1)', // error is always underlined in red
-        },
       },
       '&:before': {
         borderBottom: `1px solid ${
diff --git a/packages/mui-material/src/Input/Input.js b/packages/mui-material/src/Input/Input.js
index 9c908d55a8d950..2226c829f8a211 100644
--- a/packages/mui-material/src/Input/Input.js
+++ b/packages/mui-material/src/Input/Input.js
@@ -79,9 +79,6 @@ const InputRoot = styled(InputBaseRoot, {
         '&:before, &:after': {
           borderBottomColor: (theme.vars || theme).palette.error.main,
         },
-        '&:focus-within:after': {
-          transform: 'scaleX(1)', // error is always underlined in red
-        },
       },
       '&:before': {
         borderBottom: `1px solid ${bottomLineColor}`,
@@ -97,7 +94,7 @@ const InputRoot = styled(InputBaseRoot, {
         pointerEvents: 'none', // Transparent to the hover style.
       },
       [`&:hover:not(.${inputClasses.disabled}, .${inputClasses.error}):before`]: {
-        borderBottom: `1px solid ${(theme.vars || theme).palette.text.primary}`,
+        borderBottom: `2px solid ${(theme.vars || theme).palette.text.primary}`,
         // Reset on touch devices, it doesn't add specificity
         '@media (hover: none)': {
           borderBottom: `1px solid ${bottomLineColor}`,