diff --git a/index.js b/index.js
index 6d80316..2be1bd1 100644
--- a/index.js
+++ b/index.js
@@ -49,8 +49,8 @@ const postProcess = (input, toUpperCase) => {
 	SEPARATORS_AND_IDENTIFIER.lastIndex = 0;
 	NUMBERS_AND_IDENTIFIER.lastIndex = 0;
 
-	return input.replace(SEPARATORS_AND_IDENTIFIER, (_, identifier) => toUpperCase(identifier))
-		.replace(NUMBERS_AND_IDENTIFIER, m => toUpperCase(m));
+	return input.replace(NUMBERS_AND_IDENTIFIER, (match, pattern, offset) => ['_', '-'].includes(input.charAt(offset + match.length)) ? match : toUpperCase(match))
+		.replace(SEPARATORS_AND_IDENTIFIER, (_, identifier) => toUpperCase(identifier));
 };
 
 export default function camelCase(input, options) {
diff --git a/test.js b/test.js
index 8c3f82b..4a013f8 100644
--- a/test.js
+++ b/test.js
@@ -2,6 +2,9 @@ import test from 'ava';
 import camelCase from './index.js';
 
 test('camelCase', t => {
+	t.is(camelCase('b2b_registration_request'), 'b2bRegistrationRequest');
+	t.is(camelCase('b2b-registration-request'), 'b2bRegistrationRequest');
+	t.is(camelCase('b2b_registration_b2b_request'), 'b2bRegistrationB2bRequest');
 	t.is(camelCase('foo'), 'foo');
 	t.is(camelCase('IDs'), 'ids');
 	t.is(camelCase('FooIDs'), 'fooIds');
@@ -76,6 +79,7 @@ test('camelCase', t => {
 });
 
 test('camelCase with pascalCase option', t => {
+	t.is(camelCase('b2b_registration_request', {pascalCase: true}), 'B2bRegistrationRequest');
 	t.is(camelCase('foo', {pascalCase: true}), 'Foo');
 	t.is(camelCase('foo-bar', {pascalCase: true}), 'FooBar');
 	t.is(camelCase('foo-bar-baz', {pascalCase: true}), 'FooBarBaz');