diff --git a/src/consensus/activation.h b/src/consensus/activation.h
--- a/src/consensus/activation.h
+++ b/src/consensus/activation.h
@@ -32,4 +32,8 @@
 bool IsGravitonEnabled(const Consensus::Params &params,
                        const CBlockIndex *pindexPrev);
 
+/** Check if May 15th, 2020 protocol upgrade has activated. */
+bool IsPhononEnabled(const Consensus::Params &params,
+                     const CBlockIndex *pindexPrev);
+
 #endif // BITCOIN_CONSENSUS_ACTIVATION_H
diff --git a/src/consensus/activation.cpp b/src/consensus/activation.cpp
--- a/src/consensus/activation.cpp
+++ b/src/consensus/activation.cpp
@@ -58,3 +58,13 @@
            gArgs.GetArg("-gravitonactivationtime",
                         params.gravitonActivationTime);
 }
+
+bool IsPhononEnabled(const Consensus::Params &params,
+                     const CBlockIndex *pindexPrev) {
+    if (pindexPrev == nullptr) {
+        return false;
+    }
+
+    return pindexPrev->GetMedianTimePast() >=
+           gArgs.GetArg("-phononactivationtime", params.phononActivationTime);
+}
diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -993,6 +993,9 @@
 
     // TODO remove after the Nov 2019 upgrade
     gArgs.AddArg("-gravitonactivationtime", "", false, OptionsCategory::HIDDEN);
+
+    // TODO remove after the May 2020 upgrade
+    gArgs.AddArg("-phononactivationtime", "", false, OptionsCategory::HIDDEN);
 }
 
 std::string LicenseInfo() {
diff --git a/src/test/activation_tests.cpp b/src/test/activation_tests.cpp
--- a/src/test/activation_tests.cpp
+++ b/src/test/activation_tests.cpp
@@ -49,4 +49,30 @@
     BOOST_CHECK(IsGravitonEnabled(params, &blocks.back()));
 }
 
+BOOST_AUTO_TEST_CASE(isphononenabled) {
+    CBlockIndex prev;
+
+    const Consensus::Params &params = Params().GetConsensus();
+    const auto activation =
+        gArgs.GetArg("-phononactivationtime", params.phononActivationTime);
+    SetMockTime(activation - 1000000);
+
+    BOOST_CHECK(!IsPhononEnabled(params, nullptr));
+
+    std::array<CBlockIndex, 12> blocks;
+    for (size_t i = 1; i < blocks.size(); ++i) {
+        blocks[i].pprev = &blocks[i - 1];
+    }
+    BOOST_CHECK(!IsPhononEnabled(params, &blocks.back()));
+
+    SetMTP(blocks, activation - 1);
+    BOOST_CHECK(!IsPhononEnabled(params, &blocks.back()));
+
+    SetMTP(blocks, activation);
+    BOOST_CHECK(IsPhononEnabled(params, &blocks.back()));
+
+    SetMTP(blocks, activation + 1);
+    BOOST_CHECK(IsPhononEnabled(params, &blocks.back()));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/test_bitcoin_main.cpp b/src/test/test_bitcoin_main.cpp
--- a/src/test/test_bitcoin_main.cpp
+++ b/src/test/test_bitcoin_main.cpp
@@ -28,7 +28,10 @@
     return false;
 }
 
-std::set<std::string> testArgs = {"-gravitonactivationtime"};
+std::set<std::string> testArgs = {
+    "-gravitonactivationtime",
+    "-phononactivationtime",
+};
 
 int main(int argc, char *argv[]) {
     // Additional CLI params supported by test_bitcoin: