diff --git a/src/noConfigDebugInit.ts b/src/noConfigDebugInit.ts
index b0da4f01..2f84ee6b 100644
--- a/src/noConfigDebugInit.ts
+++ b/src/noConfigDebugInit.ts
@@ -8,6 +8,7 @@ import * as vscode from 'vscode';
 
 import { sendInfo, sendError } from "vscode-extension-telemetry-wrapper";
 import { getJavaHome } from "./utility";
+import { buildNoConfigPathAppendValue } from "./pathUtil";
 
 /**
  * Registers the configuration-less debugging setup for the extension.
@@ -91,14 +92,7 @@ export async function registerNoConfigDebug(
     }
 
     const noConfigScriptsDir = path.join(extPath, 'bundled', 'scripts', 'noConfigScripts');
-    const pathSeparator = process.platform === 'win32' ? ';' : ':';
-
-    // Check if the current PATH already ends with a path separator to avoid double separators
-    const currentPath = process.env.PATH || '';
-    const needsSeparator = currentPath.length > 0 && !currentPath.endsWith(pathSeparator);
-    const pathValueToAppend = needsSeparator ? `${pathSeparator}${noConfigScriptsDir}` : noConfigScriptsDir;
-
-    collection.append('PATH', pathValueToAppend);
+    collection.append('PATH', buildNoConfigPathAppendValue(noConfigScriptsDir));
 
     // create file system watcher for the debuggerAdapterEndpointFolder for when the communication port is written
     const fileSystemWatcher = vscode.workspace.createFileSystemWatcher(
diff --git a/src/pathUtil.ts b/src/pathUtil.ts
new file mode 100644
index 00000000..a9f680b3
--- /dev/null
+++ b/src/pathUtil.ts
@@ -0,0 +1,19 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+/**
+ * Builds the value to append to PATH for the noConfigScripts directory.
+ *
+ * `vscode.EnvironmentVariableCollection.append()` does literal string
+ * concatenation, so we always prepend a separator to avoid gluing our
+ * directory onto the last entry of the user's PATH (see issue #1637).
+ *
+ * @param platform defaults to `process.platform`; injectable for tests.
+ */
+export function buildNoConfigPathAppendValue(
+    scriptsDir: string,
+    platform: NodeJS.Platform = process.platform,
+): string {
+    const pathSeparator = platform === 'win32' ? ';' : ':';
+    return `${pathSeparator}${scriptsDir}`;
+}
diff --git a/test/pathUtil.test.ts b/test/pathUtil.test.ts
new file mode 100644
index 00000000..9f76c8f2
--- /dev/null
+++ b/test/pathUtil.test.ts
@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+import * as assert from "assert";
+
+import { buildNoConfigPathAppendValue } from "../src/pathUtil";
+
+// Regression tests for issue #1637.
+suite("buildNoConfigPathAppendValue", () => {
+
+    const winDir = "C:\\Users\\me\\.vscode\\extensions\\vscjava.vscode-java-debug-0.59.0\\bundled\\scripts\\noConfigScripts";
+    const posixDir = "/home/me/.vscode/extensions/vscjava.vscode-java-debug-0.59.0/bundled/scripts/noConfigScripts";
+
+    test("uses ';' as separator on Windows", () => {
+        const result = buildNoConfigPathAppendValue(winDir, "win32");
+        assert.strictEqual(result, `;${winDir}`);
+    });
+
+    test("uses ':' as separator on Linux", () => {
+        const result = buildNoConfigPathAppendValue(posixDir, "linux");
+        assert.strictEqual(result, `:${posixDir}`);
+    });
+
+    test("uses ':' as separator on macOS", () => {
+        const result = buildNoConfigPathAppendValue(posixDir, "darwin");
+        assert.strictEqual(result, `:${posixDir}`);
+    });
+
+    test("always starts with a path separator (Windows)", () => {
+        const result = buildNoConfigPathAppendValue(winDir, "win32");
+        assert.ok(result.startsWith(";"));
+    });
+
+    test("always starts with a path separator (POSIX)", () => {
+        const result = buildNoConfigPathAppendValue(posixDir, "linux");
+        assert.ok(result.startsWith(":"));
+    });
+
+    test("never collapses scriptsDir into the previous PATH entry on Windows", () => {
+        // #1637 scenario: last user PATH entry has no trailing separator.
+        const userPath = "C:\\foo;C:\\Program Files\\jreleaser\\";
+        const entries = (userPath + buildNoConfigPathAppendValue(winDir, "win32")).split(";");
+        assert.ok(entries.includes("C:\\Program Files\\jreleaser\\"));
+        assert.ok(entries.includes(winDir));
+    });
+
+    test("never collapses scriptsDir into the previous PATH entry on POSIX", () => {
+        const userPath = "/usr/bin:/opt/jreleaser/bin";
+        const entries = (userPath + buildNoConfigPathAppendValue(posixDir, "linux")).split(":");
+        assert.ok(entries.includes("/opt/jreleaser/bin"));
+        assert.ok(entries.includes(posixDir));
+    });
+
+    test("yields only an empty (harmless) entry when the user's PATH already ends with a separator", () => {
+        const userPath = "C:\\foo;C:\\bar;";
+        const entries = (userPath + buildNoConfigPathAppendValue(winDir, "win32")).split(";");
+        assert.ok(entries.includes(winDir));
+        assert.ok(!entries.some((e) => e !== winDir && e.endsWith(winDir)));
+    });
+
+    test("scriptsDir appears unchanged at the end of the appended value", () => {
+        const result = buildNoConfigPathAppendValue(winDir, "win32");
+        assert.ok(result.endsWith(winDir));
+    });
+});