diff --git a/mountpoint-s3-client/tests/common/mod.rs b/mountpoint-s3-client/tests/common/mod.rs
index f61960711..b81ebc334 100644
--- a/mountpoint-s3-client/tests/common/mod.rs
+++ b/mountpoint-s3-client/tests/common/mod.rs
@@ -32,6 +32,12 @@ fn init_tracing_subscriber() {
     let _ = subscriber.try_init();
 }
 
+#[ctor::ctor]
+fn init_crt() {
+    mountpoint_s3_crt::io::io_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+    mountpoint_s3_crt::s3::s3_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+}
+
 pub enum AccessPointType {
     SingleRegion,
     ObjectLambda,
diff --git a/mountpoint-s3-crt/src/io.rs b/mountpoint-s3-crt/src/io.rs
index 5b86454f0..07f222fb3 100644
--- a/mountpoint-s3-crt/src/io.rs
+++ b/mountpoint-s3-crt/src/io.rs
@@ -15,7 +15,7 @@ pub mod retry_strategy;
 static IO_LIBRARY_INIT: Once = Once::new();
 
 /// Set up the aws-c-io library using the given allocator.
-fn io_library_init(allocator: &Allocator) {
+pub fn io_library_init(allocator: &Allocator) {
     IO_LIBRARY_INIT.call_once(|| {
         // Safety: the CRT ensures this call happens only once.
         unsafe {
diff --git a/mountpoint-s3-crt/src/lib.rs b/mountpoint-s3-crt/src/lib.rs
index 3c6cb8d9d..4b2ff628d 100644
--- a/mountpoint-s3-crt/src/lib.rs
+++ b/mountpoint-s3-crt/src/lib.rs
@@ -138,6 +138,12 @@ mod test {
         tracing_subscriber::fmt::init();
     }
 
+    #[ctor::ctor]
+    fn init_crt() {
+        crate::io::io_library_init(&crate::common::allocator::Allocator::default());
+        crate::s3::s3_library_init(&crate::common::allocator::Allocator::default());
+    }
+
     /// Validate that ASan is working across both Rust and the CRT by intentionally provoking a
     /// use-after-free that crosses the boundary: the allocation is created and freed by Rust, but
     /// accessed by the CRT. Ignored by default, and run only by ASan in CI.
diff --git a/mountpoint-s3-crt/src/s3.rs b/mountpoint-s3-crt/src/s3.rs
index c10d01572..9be95762f 100644
--- a/mountpoint-s3-crt/src/s3.rs
+++ b/mountpoint-s3-crt/src/s3.rs
@@ -12,7 +12,7 @@ pub mod endpoint_resolver;
 static S3_LIBRARY_INIT: Once = Once::new();
 
 /// Set up the aws-c-io library using the given allocator.
-fn s3_library_init(allocator: &Allocator) {
+pub fn s3_library_init(allocator: &Allocator) {
     S3_LIBRARY_INIT.call_once(|| {
         // Safety: the CRT ensures this call happens only once.
         unsafe {
diff --git a/mountpoint-s3/src/lib.rs b/mountpoint-s3/src/lib.rs
index 44fd70087..084cd3cc9 100644
--- a/mountpoint-s3/src/lib.rs
+++ b/mountpoint-s3/src/lib.rs
@@ -24,3 +24,10 @@ fn init_tracing_subscriber() {
     let _ = mountpoint_s3_crt::common::rust_log_adapter::RustLogAdapter::try_init();
     let _ = tracing_subscriber::fmt::try_init();
 }
+
+#[cfg(test)]
+#[ctor::ctor]
+fn init_crt() {
+    mountpoint_s3_crt::io::io_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+    mountpoint_s3_crt::s3::s3_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+}
diff --git a/mountpoint-s3/tests/common/mod.rs b/mountpoint-s3/tests/common/mod.rs
index a43bb63b7..9b800eddc 100644
--- a/mountpoint-s3/tests/common/mod.rs
+++ b/mountpoint-s3/tests/common/mod.rs
@@ -107,3 +107,9 @@ fn init_tracing_subscriber() {
     let _ = RustLogAdapter::try_init();
     let _ = tracing_subscriber::fmt::try_init();
 }
+
+#[ctor::ctor]
+fn init_crt() {
+    mountpoint_s3_crt::io::io_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+    mountpoint_s3_crt::s3::s3_library_init(&mountpoint_s3_crt::common::allocator::Allocator::default());
+}