diff --git a/bitcoin/contrib/test.sh b/bitcoin/contrib/test.sh
index 8d8f8848..6273fbdd 100755
--- a/bitcoin/contrib/test.sh
+++ b/bitcoin/contrib/test.sh
@@ -26,6 +26,7 @@ fi
 # Pin dependencies as required if we are using MSRV toolchain.
 if cargo --version | grep "1\.48"; then
     # 1.0.157 uses syn 2.0 which requires edition 2021
+    cargo update -p serde_json --precise 1.0.99
     cargo update -p serde --precise 1.0.156
 fi
 
diff --git a/hashes/contrib/test.sh b/hashes/contrib/test.sh
index c311f531..7f8593f2 100755
--- a/hashes/contrib/test.sh
+++ b/hashes/contrib/test.sh
@@ -16,6 +16,7 @@ fi
 # Pin dependencies as required if we are using MSRV toolchain.
 if cargo --version | grep "1\.48"; then
     # 1.0.157 uses syn 2.0 which requires edition 2021
+    cargo update -p serde_json --precise 1.0.99
     cargo update -p serde --precise 1.0.156
 fi