diff --git a/bitcoin/contrib/test.sh b/bitcoin/contrib/test.sh
index 1532c21c..c3b8e914 100755
--- a/bitcoin/contrib/test.sh
+++ b/bitcoin/contrib/test.sh
@@ -31,6 +31,12 @@ if cargo --version | grep "1\.41"; then
     cargo update -p syn --precise 1.0.107
 fi
 
+# Pin dependencies as above (required for no-std tests that use Rust 1.47 toolchain).
+if cargo --version | grep "1\.47"; then
+    cargo update -p serde --precise 1.0.156
+    cargo update -p syn --precise 1.0.107
+fi
+
 # We should not have any duplicate dependencies. This catches mistakes made upgrading dependencies
 # in one crate and not in another (e.g. upgrade bitcoin_hashes in bitcoin but not in secp).
 duplicate_dependencies=$(