diff --git a/src/aws-cpp-sdk-core/source/http/URI.cpp b/src/aws-cpp-sdk-core/source/http/URI.cpp
index daf5554b7a4a..cf967c75237d 100644
--- a/src/aws-cpp-sdk-core/source/http/URI.cpp
+++ b/src/aws-cpp-sdk-core/source/http/URI.cpp
@@ -306,8 +306,14 @@ QueryStringParameterCollection URI::GetQueryStringParameters(bool decode) const
 
             //split on =
             size_t locationOfEquals = keyValuePair.find('=');
-            Aws::String key = keyValuePair.substr(0, locationOfEquals);
-            Aws::String value = keyValuePair.substr(locationOfEquals + 1);
+            Aws::String key, value;
+            if (locationOfEquals != std::string::npos) {
+                key = keyValuePair.substr(0, locationOfEquals);
+                value = keyValuePair.substr(locationOfEquals + 1);
+            }
+            else {
+                key = keyValuePair;
+            }
 
             if(decode)
             {
diff --git a/tests/aws-cpp-sdk-core-tests/http/URITest.cpp b/tests/aws-cpp-sdk-core-tests/http/URITest.cpp
index 05a4eee8613f..772f7d0276fc 100644
--- a/tests/aws-cpp-sdk-core-tests/http/URITest.cpp
+++ b/tests/aws-cpp-sdk-core-tests/http/URITest.cpp
@@ -415,3 +415,32 @@ TEST_F(URITest, TestHostParsesCorrectly) {
     uri = "https://127.0.0.1:9000";
     EXPECT_STREQ("127.0.0.1", uri.GetHost().c_str());
 }
+
+TEST_F(URITest, TestCanonicalizeValuelessQueryParameters)
+{
+    // S3 Annotations case: ?annotation + annotationName=classification
+    URI annotationUri("https://bucket.s3.us-east-2.amazonaws.com/key");
+    annotationUri.SetQueryString("?annotation");
+    annotationUri.AddQueryStringParameter("annotationName", "classification");
+    annotationUri.CanonicalizeQueryString();
+    EXPECT_EQ("?annotation=&annotationName=classification", annotationUri.GetQueryString());
+
+    // S3 Analytics case: ?analytics + id=my-config
+    URI analyticsUri("https://bucket.s3.us-east-1.amazonaws.com");
+    analyticsUri.SetQueryString("?analytics");
+    analyticsUri.AddQueryStringParameter("id", "my-config");
+    analyticsUri.CanonicalizeQueryString();
+    EXPECT_EQ("?analytics=&id=my-config", analyticsUri.GetQueryString());
+
+    // Value-less marker alone (no extra params) should remain unchanged
+    URI markerOnlyUri("https://bucket.s3.us-east-1.amazonaws.com?tagging");
+    markerOnlyUri.CanonicalizeQueryString();
+    EXPECT_EQ("?tagging", markerOnlyUri.GetQueryString());
+
+    // Value-less marker with explicit empty value should preserve =
+    URI emptyValueUri("https://bucket.s3.us-east-1.amazonaws.com");
+    emptyValueUri.SetQueryString("?annotation=");
+    emptyValueUri.AddQueryStringParameter("annotationName", "classification");
+    emptyValueUri.CanonicalizeQueryString();
+    EXPECT_EQ("?annotation=&annotationName=classification", emptyValueUri.GetQueryString());
+}
\ No newline at end of file
diff --git a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/s3/S3RestXmlCppClientGenerator.java b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/s3/S3RestXmlCppClientGenerator.java
index 40a30970937d..17bf260a0e2a 100644
--- a/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/s3/S3RestXmlCppClientGenerator.java
+++ b/tools/code-generation/generator/src/main/java/com/amazonaws/util/awsclientgenerator/generators/cpp/s3/S3RestXmlCppClientGenerator.java
@@ -174,11 +174,6 @@ public class S3RestXmlCppClientGenerator extends RestXmlCppClientGenerator {
         s3CrtEnabledOps.add("PutObject");
         s3CrtEnabledOps.add("CopyObject");
 
-        emptyValueQueryMarkerOps.add("PutObjectAnnotation");
-        emptyValueQueryMarkerOps.add("GetObjectAnnotation");
-        emptyValueQueryMarkerOps.add("ListObjectAnnotations");
-        emptyValueQueryMarkerOps.add("DeleteObjectAnnotation");
-
         bucketLocationConstraints.add("us-east-1");
         bucketLocationConstraints.add("us-east-2");
         bucketLocationConstraints.add("us-west-1");