diff --git a/install-cmake.sh b/install-cmake.sh
index 091a00c..3f59ae4 100755
--- a/install-cmake.sh
+++ b/install-cmake.sh
@@ -39,6 +39,12 @@
 
 # Define constants.
 #==============================================================================
+# Branches for github dependencies.
+#------------------------------------------------------------------------------
+SECP256K1_BRANCH="v0.5.1"
+BITCOIN_SYSTEM_BRANCH="master"
+BITCOIN_PROTOCOL_BRANCH="master"
+
 # Sentinel for comparison of sequential build.
 #------------------------------------------------------------------------------
 SEQUENTIAL=1
@@ -933,12 +939,12 @@ build_all()
     export CPPFLAGS="$CPPFLAGS ${BOOST_FLAGS[@]}"
     build_from_tarball_boost "$BOOST_ARCHIVE" "$PARALLEL" "$BUILD_BOOST" "${BOOST_OPTIONS[@]}"
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github bitcoin-core secp256k1 v0.5.1 "$BUILD_SECP256K1"
+    create_from_github bitcoin-core secp256k1 ${SECP256K1_BRANCH} "$BUILD_SECP256K1"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${SECP256K1_FLAGS[@]}"
     build_from_github secp256k1 "$PARALLEL" false "$BUILD_SECP256K1" "${SECP256K1_OPTIONS[@]}" $CUMULATIVE_FILTERED_ARGS
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github libbitcoin libbitcoin-system master "yes"
+    create_from_github libbitcoin libbitcoin-system ${BITCOIN_SYSTEM_BRANCH} "yes"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_SYSTEM_FLAGS[@]}"
     build_from_github_cmake libbitcoin-system "$PARALLEL" false "yes" "${BITCOIN_SYSTEM_OPTIONS[@]}" $CUMULATIVE_FILTERED_ARGS_CMAKE "$@"
@@ -946,7 +952,7 @@ build_all()
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_PROTOCOL_FLAGS[@]}"
     if [[ ! ($CI == true) ]]; then
-        create_from_github libbitcoin libbitcoin-protocol master "yes"
+        create_from_github libbitcoin libbitcoin-protocol ${BITCOIN_PROTOCOL_BRANCH} "yes"
         build_from_github_cmake libbitcoin-protocol "$PARALLEL" true "yes" "${BITCOIN_PROTOCOL_OPTIONS[@]}" $CUMULATIVE_FILTERED_ARGS_CMAKE "$@"
     else
         push_directory "$PRESUMED_CI_PROJECT_PATH"
diff --git a/install-cmakepresets.sh b/install-cmakepresets.sh
index bdcb0e9..3c14f53 100755
--- a/install-cmakepresets.sh
+++ b/install-cmakepresets.sh
@@ -40,6 +40,12 @@
 
 # Define constants.
 #==============================================================================
+# Branches for github dependencies.
+#------------------------------------------------------------------------------
+SECP256K1_BRANCH="v0.5.1"
+BITCOIN_SYSTEM_BRANCH="master"
+BITCOIN_PROTOCOL_BRANCH="master"
+
 
 # Declare associative array for computed presets.
 #------------------------------------------------------------------------------
@@ -972,12 +978,12 @@ build_all()
     export CPPFLAGS="$CPPFLAGS ${BOOST_FLAGS[@]}"
     build_from_tarball_boost "$BOOST_ARCHIVE" "$PARALLEL" "$BUILD_BOOST" "${BOOST_OPTIONS[@]}"
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github bitcoin-core secp256k1 v0.5.1 "$BUILD_SECP256K1"
+    create_from_github bitcoin-core secp256k1 ${SECP256K1_BRANCH} "$BUILD_SECP256K1"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${SECP256K1_FLAGS[@]}"
     build_from_github secp256k1 "$PARALLEL" false "$BUILD_SECP256K1" "${SECP256K1_OPTIONS[@]}" $CUMULATIVE_FILTERED_ARGS
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github libbitcoin libbitcoin-system master "yes"
+    create_from_github libbitcoin libbitcoin-system ${BITCOIN_SYSTEM_BRANCH} "yes"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_SYSTEM_FLAGS[@]}"
     display_message "libbitcoin-system PRESET ${REPO_PRESET[libbitcoin-system]}"
@@ -986,7 +992,7 @@ build_all()
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_PROTOCOL_FLAGS[@]}"
     if [[ ! ($CI == true) ]]; then
-        create_from_github libbitcoin libbitcoin-protocol master "yes"
+        create_from_github libbitcoin libbitcoin-protocol ${BITCOIN_PROTOCOL_BRANCH} "yes"
         display_message "libbitcoin-protocol PRESET ${REPO_PRESET[libbitcoin-protocol]}"
         build_from_github_cmake libbitcoin-protocol ${REPO_PRESET[libbitcoin-protocol]} "$PARALLEL" true             "yes" "${BITCOIN_PROTOCOL_OPTIONS[@]}" $CUMULATIVE_FILTERED_ARGS_CMAKE "$@"
     else
diff --git a/install.sh b/install.sh
index 5a875b9..11cea3a 100755
--- a/install.sh
+++ b/install.sh
@@ -39,6 +39,12 @@
 
 # Define constants.
 #==============================================================================
+# Branches for github dependencies.
+#------------------------------------------------------------------------------
+SECP256K1_BRANCH="v0.5.1"
+BITCOIN_SYSTEM_BRANCH="master"
+BITCOIN_PROTOCOL_BRANCH="master"
+
 # Sentinel for comparison of sequential build.
 #------------------------------------------------------------------------------
 SEQUENTIAL=1
@@ -808,12 +814,12 @@ build_all()
     export CPPFLAGS="$CPPFLAGS ${BOOST_FLAGS[@]}"
     build_from_tarball_boost "$BOOST_ARCHIVE" "$PARALLEL" "$BUILD_BOOST" "${BOOST_OPTIONS[@]}"
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github bitcoin-core secp256k1 v0.5.1 "$BUILD_SECP256K1"
+    create_from_github bitcoin-core secp256k1 ${SECP256K1_BRANCH} "$BUILD_SECP256K1"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${SECP256K1_FLAGS[@]}"
     build_from_github secp256k1 "$PARALLEL" false "$BUILD_SECP256K1" "${SECP256K1_OPTIONS[@]}" "$@"
     export CPPFLAGS=$SAVE_CPPFLAGS
-    create_from_github libbitcoin libbitcoin-system master "yes"
+    create_from_github libbitcoin libbitcoin-system ${BITCOIN_SYSTEM_BRANCH} "yes"
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_SYSTEM_FLAGS[@]}"
     build_from_github libbitcoin-system "$PARALLEL" false "yes" "${BITCOIN_SYSTEM_OPTIONS[@]}" "$@"
@@ -821,7 +827,7 @@ build_all()
     local SAVE_CPPFLAGS="$CPPFLAGS"
     export CPPFLAGS="$CPPFLAGS ${BITCOIN_PROTOCOL_FLAGS[@]}"
     if [[ ! ($CI == true) ]]; then
-        create_from_github libbitcoin libbitcoin-protocol master "yes"
+        create_from_github libbitcoin libbitcoin-protocol ${BITCOIN_PROTOCOL_BRANCH} "yes"
         build_from_github libbitcoin-protocol "$PARALLEL" true "yes" "${BITCOIN_PROTOCOL_OPTIONS[@]}" "$@"
     else
         push_directory "$PRESUMED_CI_PROJECT_PATH"