diff --git a/src/Makefile.am b/src/Makefile.am
index df56ac70903438..ea144da1965968 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -337,6 +337,7 @@ BITCOIN_CORE_H = \
   validation.h \
   validationinterface.h \
   versionbits.h \
+  versionbits_impl.h \
   wallet/bdb.h \
   wallet/coincontrol.h \
   wallet/coinselection.h \
diff --git a/src/test/fuzz/versionbits.cpp b/src/test/fuzz/versionbits.cpp
index f52c17cffc110d..e9aaa8eb123352 100644
--- a/src/test/fuzz/versionbits.cpp
+++ b/src/test/fuzz/versionbits.cpp
@@ -9,6 +9,7 @@
 #include <primitives/block.h>
 #include <util/chaintype.h>
 #include <versionbits.h>
+#include <versionbits_impl.h>
 
 #include <test/fuzz/FuzzedDataProvider.h>
 #include <test/fuzz/fuzz.h>
diff --git a/src/test/versionbits_tests.cpp b/src/test/versionbits_tests.cpp
index bc4cc0c87dc05e..e44088071d749c 100644
--- a/src/test/versionbits_tests.cpp
+++ b/src/test/versionbits_tests.cpp
@@ -9,6 +9,7 @@
 #include <test/util/setup_common.h>
 #include <util/chaintype.h>
 #include <versionbits.h>
+#include <versionbits_impl.h>
 
 #include <boost/test/unit_test.hpp>
 
diff --git a/src/versionbits.cpp b/src/versionbits.cpp
index 537988a1c593a8..3f6d0573e168ea 100644
--- a/src/versionbits.cpp
+++ b/src/versionbits.cpp
@@ -7,6 +7,7 @@
 #include <kernel/chainparams.h>
 #include <util/check.h>
 #include <versionbits.h>
+#include <versionbits_impl.h>
 
 ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const
 {
diff --git a/src/versionbits.h b/src/versionbits.h
index 676a2020635ce6..fa0eee4a0d95ad 100644
--- a/src/versionbits.h
+++ b/src/versionbits.h
@@ -24,18 +24,8 @@ static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
 /** Total bits available for versionbits */
 static const int32_t VERSIONBITS_NUM_BITS = 29;
 
-/** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
- *  State transitions happen during retarget period if conditions are met
- *  In case of reorg, transitions can go backward. Without transition, state is
- *  inherited between periods. All blocks of a period share the same state.
- */
-enum class ThresholdState {
-    DEFINED,   // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
-    STARTED,   // For blocks past the starttime.
-    LOCKED_IN, // For at least one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion, until min_activation_height is reached.
-    ACTIVE,    // For all blocks after the LOCKED_IN retarget period (final state)
-    FAILED,    // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
-};
+/** Opaque type for BIP9 state. See versionbits_impl.h for details. */
+enum class ThresholdState : uint8_t;
 
 // A map that gives the state for blocks whose height is a multiple of Period().
 // The map is indexed by the block's parent, however, so all keys in the map
@@ -75,30 +65,6 @@ struct BIP9GBTStatus {
     std::map<std::string, const Info> signalling, locked_in, active;
 };
 
-/**
- * Abstract class that implements BIP9-style threshold logic, and caches results.
- */
-class AbstractThresholdConditionChecker {
-protected:
-    virtual bool Condition(const CBlockIndex* pindex) const =0;
-    virtual int64_t BeginTime() const =0;
-    virtual int64_t EndTime() const =0;
-    virtual int MinActivationHeight() const { return 0; }
-    virtual int Period() const =0;
-    virtual int Threshold() const =0;
-
-public:
-    /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex
-     * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled
-     */
-    BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, std::vector<bool>* signalling_blocks = nullptr) const;
-    /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
-     *  Caches state from first block of period. */
-    ThresholdState GetStateFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
-    /** Returns the height since when the ThresholdState has started for pindex A based on parent pindexPrev B, all blocks of a period share the same */
-    int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
-};
-
 /** BIP 9 allows multiple softforks to be deployed in parallel. We cache
  *  per-period state for every one of them. */
 class VersionBitsCache
diff --git a/src/versionbits_impl.h b/src/versionbits_impl.h
new file mode 100644
index 00000000000000..df56a51818a382
--- /dev/null
+++ b/src/versionbits_impl.h
@@ -0,0 +1,52 @@
+// Copyright (c) 2016-2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_VERSIONBITS_IMPL_H
+#define BITCOIN_VERSIONBITS_IMPL_H
+
+#include <chain.h>
+#include <sync.h>
+#include <versionbits.h>
+
+#include <array>
+#include <map>
+
+/** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
+ *  State transitions happen during retarget period if conditions are met
+ *  In case of reorg, transitions can go backward. Without transition, state is
+ *  inherited between periods. All blocks of a period share the same state.
+ */
+enum class ThresholdState : uint8_t {
+    DEFINED,   // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
+    STARTED,   // For blocks past the starttime.
+    LOCKED_IN, // For at least one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion, until min_activation_height is reached.
+    ACTIVE,    // For all blocks after the LOCKED_IN retarget period (final state)
+    FAILED,    // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
+};
+
+/**
+ * Abstract class that implements BIP9-style threshold logic, and caches results.
+ */
+class AbstractThresholdConditionChecker {
+protected:
+    virtual bool Condition(const CBlockIndex* pindex) const =0;
+    virtual int64_t BeginTime() const =0;
+    virtual int64_t EndTime() const =0;
+    virtual int MinActivationHeight() const { return 0; }
+    virtual int Period() const =0;
+    virtual int Threshold() const =0;
+
+public:
+    /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex
+     * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled
+     */
+    BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, std::vector<bool>* signalling_blocks = nullptr) const;
+    /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
+     *  Caches state from first block of period. */
+    ThresholdState GetStateFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
+    /** Returns the height since when the ThresholdState has started for pindex A based on parent pindexPrev B, all blocks of a period share the same */
+    int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
+};
+
+#endif // BITCOIN_VERSIONBITS_IMPL_H