diff --git a/src/test/versionbits_tests.cpp b/src/test/versionbits_tests.cpp
--- a/src/test/versionbits_tests.cpp
+++ b/src/test/versionbits_tests.cpp
@@ -114,7 +114,7 @@
                 BOOST_CHECK_MESSAGE(
                     checker[i].GetStateFor(vpblock.empty() ? nullptr
                                                            : vpblock.back()) ==
-                        THRESHOLD_DEFINED,
+                        ThresholdState::DEFINED,
                     strprintf("Test %i for DEFINED", num));
             }
         }
@@ -128,7 +128,7 @@
                 BOOST_CHECK_MESSAGE(
                     checker[i].GetStateFor(vpblock.empty() ? nullptr
                                                            : vpblock.back()) ==
-                        THRESHOLD_STARTED,
+                        ThresholdState::STARTED,
                     strprintf("Test %i for STARTED", num));
             }
         }
@@ -142,7 +142,7 @@
                 BOOST_CHECK_MESSAGE(
                     checker[i].GetStateFor(vpblock.empty() ? nullptr
                                                            : vpblock.back()) ==
-                        THRESHOLD_LOCKED_IN,
+                        ThresholdState::LOCKED_IN,
                     strprintf("Test %i for LOCKED_IN", num));
             }
         }
@@ -156,7 +156,7 @@
                 BOOST_CHECK_MESSAGE(
                     checker[i].GetStateFor(vpblock.empty() ? nullptr
                                                            : vpblock.back()) ==
-                        THRESHOLD_ACTIVE,
+                        ThresholdState::ACTIVE,
                     strprintf("Test %i for ACTIVE", num));
             }
         }
@@ -170,7 +170,7 @@
                 BOOST_CHECK_MESSAGE(
                     checker[i].GetStateFor(vpblock.empty() ? nullptr
                                                            : vpblock.back()) ==
-                        THRESHOLD_FAILED,
+                        ThresholdState::FAILED,
                     strprintf("Test %i for FAILED", num));
             }
         }
diff --git a/src/versionbits.h b/src/versionbits.h
--- a/src/versionbits.h
+++ b/src/versionbits.h
@@ -17,12 +17,12 @@
 /** Total bits available for versionbits */
 static const int32_t VERSIONBITS_NUM_BITS = 29;
 
-enum ThresholdState {
-    THRESHOLD_DEFINED,
-    THRESHOLD_STARTED,
-    THRESHOLD_LOCKED_IN,
-    THRESHOLD_ACTIVE,
-    THRESHOLD_FAILED,
+enum class ThresholdState {
+    DEFINED,
+    STARTED,
+    LOCKED_IN,
+    ACTIVE,
+    FAILED,
 };
 
 // A map that gives the state for blocks whose height is a multiple of Period().
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -36,13 +36,13 @@
     while (cache.count(pindexPrev) == 0) {
         if (pindexPrev == nullptr) {
             // The genesis block is by definition defined.
-            cache[pindexPrev] = THRESHOLD_DEFINED;
+            cache[pindexPrev] = ThresholdState::DEFINED;
             break;
         }
         if (pindexPrev->GetMedianTimePast() < nTimeStart) {
             // Optimization: don't recompute down further, as we know every
             // earlier block will be before the start time
-            cache[pindexPrev] = THRESHOLD_DEFINED;
+            cache[pindexPrev] = ThresholdState::DEFINED;
             break;
         }
         vToCompute.push_back(pindexPrev);
@@ -60,17 +60,17 @@
         vToCompute.pop_back();
 
         switch (state) {
-            case THRESHOLD_DEFINED: {
+            case ThresholdState::DEFINED: {
                 if (pindexPrev->GetMedianTimePast() >= nTimeTimeout) {
-                    stateNext = THRESHOLD_FAILED;
+                    stateNext = ThresholdState::FAILED;
                 } else if (pindexPrev->GetMedianTimePast() >= nTimeStart) {
-                    stateNext = THRESHOLD_STARTED;
+                    stateNext = ThresholdState::STARTED;
                 }
                 break;
             }
-            case THRESHOLD_STARTED: {
+            case ThresholdState::STARTED: {
                 if (pindexPrev->GetMedianTimePast() >= nTimeTimeout) {
-                    stateNext = THRESHOLD_FAILED;
+                    stateNext = ThresholdState::FAILED;
                     break;
                 }
                 // We need to count
@@ -83,17 +83,17 @@
                     pindexCount = pindexCount->pprev;
                 }
                 if (count >= nThreshold) {
-                    stateNext = THRESHOLD_LOCKED_IN;
+                    stateNext = ThresholdState::LOCKED_IN;
                 }
                 break;
             }
-            case THRESHOLD_LOCKED_IN: {
+            case ThresholdState::LOCKED_IN: {
                 // Always progresses into ACTIVE.
-                stateNext = THRESHOLD_ACTIVE;
+                stateNext = ThresholdState::ACTIVE;
                 break;
             }
-            case THRESHOLD_FAILED:
-            case THRESHOLD_ACTIVE: {
+            case ThresholdState::FAILED:
+            case ThresholdState::ACTIVE: {
                 // Nothing happens, these are terminal states.
                 break;
             }
@@ -111,7 +111,7 @@
 
     // BIP 9 about state DEFINED: "The genesis block is by definition in this
     // state for each deployment."
-    if (initialState == THRESHOLD_DEFINED) {
+    if (initialState == ThresholdState::DEFINED) {
         return 0;
     }