diff --git a/driver-core/src/main/com/mongodb/ConnectionString.java b/driver-core/src/main/com/mongodb/ConnectionString.java
index 062ca1d45c..659e8fd02a 100644
--- a/driver-core/src/main/com/mongodb/ConnectionString.java
+++ b/driver-core/src/main/com/mongodb/ConnectionString.java
@@ -56,6 +56,7 @@
 import static com.mongodb.internal.connection.OidcAuthenticator.OidcValidator.validateCreateOidcCredential;
 import static java.lang.String.format;
 import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static java.util.Collections.unmodifiableList;
 
@@ -505,7 +506,7 @@ public ConnectionString(final String connectionString, @Nullable final DnsClient
             throw new IllegalArgumentException("srvMaxHosts can not be specified with replica set name");
         }
 
-        validateProxyParameters();
+        validateProxyParameters(combinedOptionsMaps);
 
         credential = createCredentials(combinedOptionsMaps, userName, password);
         warnOnUnsupportedOptions(combinedOptionsMaps);
@@ -1226,7 +1227,7 @@ private void validatePort(final String port) {
         }
     }
 
-    private void validateProxyParameters() {
+    private void validateProxyParameters(final Map<String, List<String>> optionsMap) {
         if (proxyHost == null) {
             if (proxyPort != null) {
                 throw new IllegalArgumentException("proxyPort can only be specified with proxyHost");
@@ -1259,6 +1260,23 @@ private void validateProxyParameters() {
             throw new IllegalArgumentException(
                     "Both proxyUsername and proxyPassword must be set together. They cannot be set individually");
         }
+
+        if (containsDuplicatedOptions("proxyhost", optionsMap)) {
+            throw new IllegalArgumentException("Duplicated values for proxyHost: " + optionsMap.get("proxyhost"));
+        }
+        if (containsDuplicatedOptions("proxyport", optionsMap)) {
+            throw new IllegalArgumentException("Duplicated values for proxyPort: " + optionsMap.get("proxyport"));
+        }
+        if (containsDuplicatedOptions("proxypassword", optionsMap)) {
+            throw new IllegalArgumentException("Duplicated values for proxyPassword: " + optionsMap.get("proxypassword"));
+        }
+        if (containsDuplicatedOptions("proxyusername", optionsMap)) {
+            throw new IllegalArgumentException("Duplicated values for proxyUsername: " + optionsMap.get("proxyusername"));
+        }
+    }
+
+    private static boolean containsDuplicatedOptions(final String optionName, final Map<String, List<String>> optionsMap) {
+        return optionsMap.getOrDefault(optionName, emptyList()).size() > 1;
     }
 
     private int countOccurrences(final String haystack, final String needle) {
diff --git a/driver-core/src/test/unit/com/mongodb/UriOptionsTest.java b/driver-core/src/test/unit/com/mongodb/UriOptionsTest.java
index d3cb925ead..736e3f5d20 100644
--- a/driver-core/src/test/unit/com/mongodb/UriOptionsTest.java
+++ b/driver-core/src/test/unit/com/mongodb/UriOptionsTest.java
@@ -47,9 +47,6 @@ public void shouldPassAllOutcomes() {
         // No CANONICALIZE_HOST_NAME support https://jira.mongodb.org/browse/JAVA-4278
         assumeFalse(getDescription().equals("Valid auth options are parsed correctly (GSSAPI)"));
 
-        // https://jira.mongodb.org/browse/JAVA-5834
-        assumeFalse(getFilename().equals("proxy-options.json"));
-
         if (getDefinition().getBoolean("valid", BsonBoolean.TRUE).getValue()) {
             testValidOptions();
         } else {