diff --git a/include/uv.h b/include/uv.h
index 7604d15f..65aa32db 100644
--- a/include/uv.h
+++ b/include/uv.h
@@ -2124,7 +2124,7 @@ UV_EXTERN int uv_dlsym(uv_lib_t* lib, const char* name, void** ptr);
 /*
  * Returns the last uv_dlopen() or uv_dlsym() error message.
  */
-UV_EXTERN const char* uv_dlerror(uv_lib_t* lib);
+UV_EXTERN const char* uv_dlerror(const uv_lib_t* lib);
 
 /*
  * The mutex functions return 0 on success or an error code < 0
diff --git a/src/unix/dl.c b/src/unix/dl.c
index cbffe4aa..ad45fc83 100644
--- a/src/unix/dl.c
+++ b/src/unix/dl.c
@@ -59,7 +59,7 @@ int uv_dlsym(uv_lib_t* lib, const char* name, void** ptr) {
 }
 
 
-const char* uv_dlerror(uv_lib_t* lib) {
+const char* uv_dlerror(const uv_lib_t* lib) {
   return lib->errmsg ? lib->errmsg : "no error";
 }
 
diff --git a/src/win/dl.c b/src/win/dl.c
index d5b8f7c7..2ef1f6c5 100644
--- a/src/win/dl.c
+++ b/src/win/dl.c
@@ -64,7 +64,7 @@ int uv_dlsym(uv_lib_t* lib, const char* name, void** ptr) {
 }
 
 
-const char* uv_dlerror(uv_lib_t* lib) {
+const char* uv_dlerror(const uv_lib_t* lib) {
   return lib->errmsg ? lib->errmsg : "no error";
 }