diff --git a/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/template/OpenApiNamespaceResolver.java b/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/template/OpenApiNamespaceResolver.java
index 7576290dd..de87fff99 100644
--- a/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/template/OpenApiNamespaceResolver.java
+++ b/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/template/OpenApiNamespaceResolver.java
@@ -1,7 +1,7 @@
 package io.quarkiverse.openapi.generator.deployment.template;
 
-import java.io.File;
 import java.lang.reflect.Method;
+import java.net.URI;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -61,7 +61,7 @@ public boolean genDeprecatedApiAttr(final String pkg, final String classname,
 
     @SuppressWarnings("unused")
     public String parseUri(String uri) {
-        return OpenApiGeneratorOutputPaths.getRelativePath(Path.of(uri)).toString().replace(File.separatorChar, '/');
+        return OpenApiGeneratorOutputPaths.getRelativePath(Path.of(URI.create(uri))).toString();
     }
 
     @SuppressWarnings("unused")
diff --git a/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapper.java b/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapper.java
index 3b1320afb..ee9b94e21 100644
--- a/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapper.java
+++ b/client/deployment/src/main/java/io/quarkiverse/openapi/generator/deployment/wrapper/OpenApiClientGeneratorWrapper.java
@@ -64,7 +64,8 @@ public abstract class OpenApiClientGeneratorWrapper {
         GlobalSettings.setProperty(ONCE_LOGGER, verbose ? FALSE.toString() : TRUE.toString());
 
         this.configurator = configurator;
-        this.configurator.setInputSpec(specFilePath.toString());
+        // toUri() for the input first to ensure consistent path names which became an issue with the 3.1.0 spec-parser
+        this.configurator.setInputSpec(specFilePath.toUri().toString());
         this.configurator.setOutputDir(outputDir.toString());
         this.configurator.addAdditionalProperty(QUARKUS_GENERATOR_NAME,
                 Collections.singletonMap("openApiSpecId", getSanitizedFileName(specFilePath)));