diff --git a/Cargo.toml b/Cargo.toml
index 33322a04..062adc6f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,10 @@ exclude = [".*"]
 # use std to retrieve OS error descriptions
 std = []
 
+# Use the custom backend on unsupported targets
+# WARNING: this feature SHOULD be enabled only by fallback implementation crates!
+custom-fallback = []
+
 # Optional backend: wasm_js
 # This flag enables the backend but does not select it. To use the backend, use
 # this flag *and* set getrandom_backend=wasm_js (see README).
diff --git a/src/backends.rs b/src/backends.rs
index d7b73cec..dbd22e05 100644
--- a/src/backends.rs
+++ b/src/backends.rs
@@ -182,6 +182,9 @@ cfg_if! {
     } else if #[cfg(all(target_arch = "x86_64", target_env = "sgx"))] {
         mod rdrand;
         pub use rdrand::*;
+    } else if #[cfg(feature = "custom-fallback")] {
+        mod custom;
+        pub use custom::*;
     } else if #[cfg(all(target_arch = "wasm32", any(target_os = "unknown", target_os = "none")))] {
         compile_error!(concat!(
             "The wasm32-unknown-unknown targets are not supported by default; \