diff --git a/Makefile.uk b/Makefile.uk
index 0141947..b59b6de 100644
--- a/Makefile.uk
+++ b/Makefile.uk
@@ -39,6 +39,15 @@ endif
 APPELFLOADER_RUST_LIB := \
 	$(APPELFLOADER_RUST_OUT)/$(APPELFLOADER_RUST_TARGET)/release/libelfloader_rs.a
 
+# Kconfig symbols the Rust side needs at *compile* time, because they decide
+# which C the archive is allowed to reference. CONFIG_APPELFLOADER_ELF_BINFMT
+# guards the `uk_binfmt_loader_args` accessors in glue/shim.c, so `binfmt.rs`
+# has to be compiled out with them.
+APPELFLOADER_RUST_FEATURES-$(CONFIG_APPELFLOADER_ELF_BINFMT) += binfmt
+
+APPELFLOADER_RUST_FEATURE_FLAGS := $(if $(APPELFLOADER_RUST_FEATURES-y), \
+	--features $(subst $(space),$(comma),$(strip $(APPELFLOADER_RUST_FEATURES-y))))
+
 APPELFLOADER_RUST_SRCS := \
 	$(wildcard $(APPELFLOADER_RUST_DIR)/src/*.rs) \
 	$(APPELFLOADER_RUST_DIR)/Cargo.toml \
@@ -61,6 +70,7 @@ $(APPELFLOADER_RUST_LIB): $(APPELFLOADER_RUST_SRCS)
 			--manifest-path $(APPELFLOADER_RUST_DIR)/Cargo.toml \
 			--target $(APPELFLOADER_RUST_TARGET) \
 			--target-dir $(APPELFLOADER_RUST_OUT) \
+			$(APPELFLOADER_RUST_FEATURE_FLAGS) \
 			--release --locked --offline)
 
 APPELFLOADER_ALIBS-y += $(APPELFLOADER_RUST_LIB)
diff --git a/rust/Cargo.toml b/rust/Cargo.toml
index b1e4ae0..01eac02 100644
--- a/rust/Cargo.toml
+++ b/rust/Cargo.toml
@@ -12,6 +12,12 @@ name = "elfloader_rs"
 # the modules that talk to Unikraft are gated on `not(test)`.
 crate-type = ["staticlib"]
 
+[features]
+# Compile the `libukbinfmt` loader. Mirrors CONFIG_APPELFLOADER_ELF_BINFMT,
+# which is what guards the matching accessors in `glue/shim.c`; the two must
+# agree or the archive references C functions that were never compiled.
+binfmt = []
+
 [dependencies]
 
 [profile.release]
diff --git a/rust/src/lib.rs b/rust/src/lib.rs
index 3dc621f..46e019b 100644
--- a/rust/src/lib.rs
+++ b/rust/src/lib.rs
@@ -45,7 +45,11 @@ mod testutil;
 
 #[cfg(not(test))]
 mod app;
-#[cfg(not(test))]
+// The accessors this module calls live behind `#if CONFIG_APPELFLOADER_ELF_BINFMT`
+// in `glue/shim.c`, so compiling it when that option is off leaves the archive
+// with undefined references to C that was never built. `Makefile.uk` turns the
+// feature on from the same Kconfig symbol that guards the C side.
+#[cfg(all(not(test), feature = "binfmt"))]
 mod binfmt;
 #[cfg(not(test))]
 mod rt;