diff --git a/configure.ac b/configure.ac
index d281903fcc..1a780d3c3b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -57,6 +57,8 @@ AC_ARG_ENABLE(memory-sentinels,
    AS_HELP_STRING(--disable-memory-sentinels, [disable code that tries to prevent some kinds of memory access bugs. For fuzzing only.]))
 AC_ARG_ENABLE(rust,
    AS_HELP_STRING(--enable-rust, [enable rust integration]))
+AC_ARG_ENABLE(cargo-online-mode,
+   AS_HELP_STRING(--enable-cargo-online-mode, [Allow cargo to make network requests to fetch crates. For builds with rust only.]))
 
 if test "x$enable_coverage" != "xyes" -a "x$enable_asserts_in_tests" = "xno" ; then
     AC_MSG_ERROR([Can't disable assertions outside of coverage build])
@@ -267,6 +269,12 @@ if test "x$enable_rust" = "xyes"; then
   fi
 
   AC_DEFINE([HAVE_RUST], 1, [have Rust])
+  if test "x$enable_cargo_online_mode" = "xyes"; then
+    CARGO_ONLINE=
+  else
+    CARGO_ONLINE=--frozen
+  fi
+  AC_SUBST(CARGO_ONLINE)
 fi
 
 ifdef([AC_C_FLEXIBLE_ARRAY_MEMBER], [
diff --git a/src/rust/tor_util/include.am b/src/rust/tor_util/include.am
index 3b877649a3..863046b929 100644
--- a/src/rust/tor_util/include.am
+++ b/src/rust/tor_util/include.am
@@ -7,6 +7,6 @@ EXTRA_DIST +=\
 src/rust/target/release/libtor_util.a: FORCE
 	( cd "$(abs_top_srcdir)/src/rust/tor_util" ; \
 		CARGO_TARGET_DIR="$(abs_top_builddir)/src/rust/target" \
-		$(CARGO) build --release --quiet --frozen )
+		$(CARGO) build --release --quiet $(CARGO_ONLINE) )
 
 FORCE:
diff --git a/src/test/include.am b/src/test/include.am
index 5fd61dd3e6..c0aca8afe2 100644
--- a/src/test/include.am
+++ b/src/test/include.am
@@ -7,7 +7,8 @@ TESTS_ENVIRONMENT = \
 	export abs_top_srcdir="$(abs_top_srcdir)"; \
 	export builddir="$(builddir)"; \
 	export TESTING_TOR_BINARY="$(TESTING_TOR_BINARY)"; \
-	export CARGO="$(CARGO)";
+	export CARGO="$(CARGO)"; \
+	export CARGO_ONLINE="$(CARGO_ONLINE)";
 
 TESTSCRIPTS = \
 	src/test/fuzz_static_testcases.sh \
diff --git a/src/test/test_rust.sh b/src/test/test_rust.sh
index b41be978b9..7c71008e02 100755
--- a/src/test/test_rust.sh
+++ b/src/test/test_rust.sh
@@ -7,7 +7,7 @@ exitcode=0
 
 for crate in $crates; do
     cd "${abs_top_srcdir:-.}/src/rust/${crate}"
-    "${CARGO:-cargo}" test --frozen || exitcode=1
+    "${CARGO:-cargo}" test ${CARGO_ONLINE-"--frozen"} || exitcode=1
 done
 
 exit $exitcode