--- a/config/rules.mk
+++ b/config/rules.mk
@@ -954,16 +954,17 @@ endif
 
 CARGO_BUILD = env $(rustflags_override) \
 	CARGO_TARGET_DIR=$(CARGO_TARGET_DIR) \
 	RUSTC=$(RUSTC) \
 	MOZ_DIST=$(ABS_DIST) \
 	LIBCLANG_PATH=$(MOZ_LIBCLANG_PATH) \
 	CLANG_PATH=$(MOZ_CLANG_PATH) \
 	PKG_CONFIG_ALLOW_CROSS=1 \
+	RUST_BACKTRACE=1 \
 	$(CARGO) build $(cargo_build_flags)
 
 ifdef RUST_LIBRARY_FILE
 
 ifdef RUST_LIBRARY_FEATURES
 rust_features_flag := --features "$(RUST_LIBRARY_FEATURES)"
 endif