diff --git a/packages/variable-resolver/src/browser/common-variable-contribution.ts b/packages/variable-resolver/src/browser/common-variable-contribution.ts
index 318f87d3c32a3..a23ee1c2bfdc8 100644
--- a/packages/variable-resolver/src/browser/common-variable-contribution.ts
+++ b/packages/variable-resolver/src/browser/common-variable-contribution.ts
@@ -18,6 +18,7 @@ import { injectable, inject } from 'inversify';
 import { VariableContribution, VariableRegistry } from './variable';
 import { EnvVariablesServer } from '@theia/core/lib/common/env-variables';
 import { CommandService } from '@theia/core/lib/common/command';
+import { isWindows } from '@theia/core/lib/common/os';
 import { PreferenceService } from '@theia/core/lib/browser/preferences/preference-service';
 import { ResourceContextKey } from '@theia/core/lib/browser/resource-context-key';
 import { VariableInput } from './variable-input';
@@ -129,6 +130,10 @@ export class CommonVariableContribution implements VariableContribution {
                 return undefined;
             }
         });
+        variables.registerVariable({
+            name: 'pathSeparator',
+            resolve: () => isWindows ? '\\' : '/'
+        });
     }
 
 }