diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index 069d0b7044..94805de7bc 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -22,3 +22,9 @@ message = "Support Sigv4 signature generation on PowerPC 32 and 64 bit. This arc
 references = ["smithy-rs#1847"]
 meta = { "breaking" = true, "tada" = false, "bug" = true }
 author = "crisidev"
+
+[[smithy-rs]]
+message = "Replace bool with enum for a function parameter of `label::fmt_string`."
+references = ["smithy-rs#1875"]
+meta = { "breaking" = true, "tada" = false, "bug" = false, "target" = "client" }
+author = "ysaito1001"
diff --git a/aws/rust-runtime/aws-sigv4/src/http_request/url_escape.rs b/aws/rust-runtime/aws-sigv4/src/http_request/url_escape.rs
index 3a9114c6eb..651c62c44a 100644
--- a/aws/rust-runtime/aws-sigv4/src/http_request/url_escape.rs
+++ b/aws/rust-runtime/aws-sigv4/src/http_request/url_escape.rs
@@ -10,5 +10,5 @@ pub(super) fn percent_encode_query(value: &str) -> String {
 }
 
 pub(super) fn percent_encode_path(value: &str) -> String {
-    label::fmt_string(value, true)
+    label::fmt_string(value, label::EncodingStrategy::Greedy)
 }
diff --git a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/RequestBindingGenerator.kt b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/RequestBindingGenerator.kt
index 9a55d74a48..dafaeea252 100644
--- a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/RequestBindingGenerator.kt
+++ b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/generators/http/RequestBindingGenerator.kt
@@ -261,7 +261,12 @@ class RequestBindingGenerator(
         when {
             target.isStringShape -> {
                 val func = format(RuntimeType.LabelFormat(runtimeConfig, "fmt_string"))
-                rust("let $outputVar = $func($input, ${label.isGreedyLabel});")
+                val encodingStrategy = if (label.isGreedyLabel) {
+                    RuntimeType.LabelFormat(runtimeConfig, "EncodingStrategy::Greedy")
+                } else {
+                    RuntimeType.LabelFormat(runtimeConfig, "EncodingStrategy::Default")
+                }
+                rust("let $outputVar = $func($input, #T);", encodingStrategy)
             }
             target.isTimestampShape -> {
                 val timestampFormat =
diff --git a/rust-runtime/aws-smithy-http/src/label.rs b/rust-runtime/aws-smithy-http/src/label.rs
index e2bf57aa9a..a4742aa0c6 100644
--- a/rust-runtime/aws-smithy-http/src/label.rs
+++ b/rust-runtime/aws-smithy-http/src/label.rs
@@ -13,32 +13,47 @@ use percent_encoding::AsciiSet;
 
 const GREEDY: &AsciiSet = &BASE_SET.remove(b'/');
 
-pub fn fmt_string<T: AsRef<str>>(t: T, greedy: bool) -> String {
-    let uri_set = if greedy { GREEDY } else { BASE_SET };
+#[non_exhaustive]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub enum EncodingStrategy {
+    Default,
+    Greedy,
+}
+
+pub fn fmt_string<T: AsRef<str>>(t: T, strategy: EncodingStrategy) -> String {
+    let uri_set = if strategy == EncodingStrategy::Greedy {
+        GREEDY
+    } else {
+        BASE_SET
+    };
     percent_encoding::utf8_percent_encode(t.as_ref(), uri_set).to_string()
 }
 
 pub fn fmt_timestamp(t: &DateTime, format: Format) -> Result<String, DateTimeFormatError> {
-    Ok(crate::query::fmt_string(t.fmt(format)?))
+    Ok(fmt_string(t.fmt(format)?, EncodingStrategy::Default))
 }
 
 #[cfg(test)]
 mod test {
-    use crate::label::fmt_string;
+    use crate::label::{fmt_string, EncodingStrategy};
     use http::Uri;
     use proptest::proptest;
 
     #[test]
     fn greedy_params() {
-        assert_eq!(fmt_string("a/b", false), "a%2Fb");
-        assert_eq!(fmt_string("a/b", true), "a/b");
+        assert_eq!(fmt_string("a/b", EncodingStrategy::Default), "a%2Fb");
+        assert_eq!(fmt_string("a/b", EncodingStrategy::Greedy), "a/b");
     }
 
     proptest! {
         #[test]
         fn test_encode_request(s: String) {
-            let _: Uri = format!("http://host.example.com/{}", fmt_string(&s, false)).parse().expect("all strings should be encoded properly");
-            let _: Uri = format!("http://host.example.com/{}", fmt_string(&s, true)).parse().expect("all strings should be encoded properly");
+            let _: Uri = format!("http://host.example.com/{}", fmt_string(&s, EncodingStrategy::Default))
+                .parse()
+                .expect("all strings should be encoded properly");
+            let _: Uri = format!("http://host.example.com/{}", fmt_string(&s, EncodingStrategy::Greedy))
+                .parse()
+                .expect("all strings should be encoded properly");
         }
     }
 }
diff --git a/rust-runtime/aws-smithy-http/src/urlencode.rs b/rust-runtime/aws-smithy-http/src/urlencode.rs
index 8129b1b185..cf97935f60 100644
--- a/rust-runtime/aws-smithy-http/src/urlencode.rs
+++ b/rust-runtime/aws-smithy-http/src/urlencode.rs
@@ -6,7 +6,7 @@
 use percent_encoding::{AsciiSet, CONTROLS};
 
 /// base set of characters that must be URL encoded
-pub const BASE_SET: &AsciiSet = &CONTROLS
+pub(crate) const BASE_SET: &AsciiSet = &CONTROLS
     .add(b' ')
     .add(b'/')
     // RFC-3986 §3.3 allows sub-delims (defined in section2.2) to be in the path component.