diff --git a/chrome/content/zotero/xpcom/utilities_internal.js b/chrome/content/zotero/xpcom/utilities_internal.js
index 4626eeadb9..4db6548716 100644
--- a/chrome/content/zotero/xpcom/utilities_internal.js
+++ b/chrome/content/zotero/xpcom/utilities_internal.js
@@ -3039,9 +3039,18 @@ Zotero.Utilities.Internal.OpenURL = {
 		);
 		if (co) {
 			let base = Zotero.Prefs.get("openURL.resolver");
-			// Add & if there's already a ?
-			let splice = base.indexOf("?") == -1 ? "?" : "&";
-			return base + splice + co;
+			if (!base.endsWith('?')) {
+				if (base.includes('login?url=')) {
+					base += '?';
+				}
+				else if (base.includes('?')) {
+					base += '&';
+				}
+				else {
+					base += '?';
+				}
+			}
+			return base + co;
 		}
 		return false;
 	},
diff --git a/test/tests/utilities_internalTest.js b/test/tests/utilities_internalTest.js
index 3f3c413c84..e4b4b0bc0a 100644
--- a/test/tests/utilities_internalTest.js
+++ b/test/tests/utilities_internalTest.js
@@ -738,4 +738,42 @@ describe("Zotero.Utilities.Internal", function () {
 			assert.equal(html, 'yes1yes2 yes3');
 		});
 	});
+	
+	describe("OpenURL", function () {
+		var item;
+		
+		before(async function () {
+			item = await createDataObject('item', { title: 'Foo Bar', date: '2024-12-19' });
+		})
+		
+		after(function () {
+			Zotero.Prefs.clear('openURL.resolver');
+		});
+		
+		describe("#resolve()", function () {
+			it("should add trailing '?' if no query string", async function () {
+				Zotero.Prefs.set("openURL.resolver", "https://resolver.ebsco.com/c/abcdef/result");
+				var url = Zotero.Utilities.Internal.OpenURL.resolve(item);
+				assert.include(url, 'result?url_ver=Z39.88-2004');
+			});
+			
+			it("should add trailing '&' if already a query string", async function () {
+				Zotero.Prefs.set("openURL.resolver", "https://resolver.ebscohost.com/openurl?custid=abcdef&groupid=main&profile=ftf&authtype=ip,uid");
+				var url = Zotero.Utilities.Internal.OpenURL.resolve(item);
+				assert.include(url, 'authtype=ip,uid&url_ver=Z39.88-2004');
+			});
+			
+			it("should add trailing '?' after /login?url=", async function () {
+				Zotero.Prefs.set("openURL.resolver", "https://proxy.school.edu/login?url=https://resolver.ebscohost.com/openurl");
+				var url = Zotero.Utilities.Internal.OpenURL.resolve(item);
+				assert.include(url, 'openurl?url_ver=Z39.88-2004');
+			});
+			
+			it("shouldn't add trailing '?' after /login?url= if URL already ends in '?'", async function () {
+				Zotero.Prefs.set("openURL.resolver", "https://proxy.school.edu/login?url=https://resolver.ebscohost.com/openurl?");
+				var url = Zotero.Utilities.Internal.OpenURL.resolve(item);
+				assert.include(url, 'openurl?url_ver=Z39.88-2004');
+			});
+		});
+	});
 });