diff --git a/hist/histv7/inc/ROOT/RAxes.hxx b/hist/histv7/inc/ROOT/RAxes.hxx
index 5e748e2c75673..682071bcd84a1 100644
--- a/hist/histv7/inc/ROOT/RAxes.hxx
+++ b/hist/histv7/inc/ROOT/RAxes.hxx
@@ -12,7 +12,6 @@
 #include "RVariableBinAxis.hxx"
 
 #include <array>
-#include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <stdexcept>
diff --git a/hist/histv7/inc/ROOT/RBinIndexRange.hxx b/hist/histv7/inc/ROOT/RBinIndexRange.hxx
index a566d0908a6ab..bee42f15c6c24 100644
--- a/hist/histv7/inc/ROOT/RBinIndexRange.hxx
+++ b/hist/histv7/inc/ROOT/RBinIndexRange.hxx
@@ -8,6 +8,7 @@
 #include "RBinIndex.hxx"
 
 #include <cassert>
+#include <cstddef> // for std::ptrdiff_t
 #include <cstdint>
 #include <iterator>
 
diff --git a/hist/histv7/inc/ROOT/RHist.hxx b/hist/histv7/inc/ROOT/RHist.hxx
index 84de3c8a33e38..12b22bad970c7 100644
--- a/hist/histv7/inc/ROOT/RHist.hxx
+++ b/hist/histv7/inc/ROOT/RHist.hxx
@@ -5,13 +5,14 @@
 #ifndef ROOT_RHist
 #define ROOT_RHist
 
+#include "RAxes.hxx" // for RAxisVariant
 #include "RBinIndex.hxx"
 #include "RHistEngine.hxx"
 #include "RHistStats.hxx"
+#include "RRegularAxis.hxx"
 #include "RWeight.hxx"
 
 #include <array>
-#include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <stdexcept>
@@ -90,21 +91,21 @@ public:
    ///
    /// Copying all bin contents can be an expensive operation, depending on the number of bins. If required, users can
    /// explicitly call Clone().
-   RHist(const RHist<BinContentType> &) = delete;
+   RHist(const RHist &) = delete;
    /// Efficiently move construct a histogram.
    ///
    /// After this operation, the moved-from object is invalid.
-   RHist(RHist<BinContentType> &&) = default;
+   RHist(RHist &&) = default;
 
    /// The copy assignment operator is deleted.
    ///
    /// Copying all bin contents can be an expensive operation, depending on the number of bins. If required, users can
    /// explicitly call Clone().
-   RHist<BinContentType> &operator=(const RHist<BinContentType> &) = delete;
+   RHist &operator=(const RHist &) = delete;
    /// Efficiently move a histogram.
    ///
    /// After this operation, the moved-from object is invalid.
-   RHist<BinContentType> &operator=(RHist<BinContentType> &&) = default;
+   RHist &operator=(RHist &&) = default;
 
    ~RHist() = default;
 
@@ -177,7 +178,7 @@ public:
    /// Throws an exception if the axes configurations are not identical.
    ///
    /// \param[in] other another histogram
-   void Add(const RHist<BinContentType> &other)
+   void Add(const RHist &other)
    {
       fEngine.Add(other.fEngine);
       fStats.Add(other.fStats);
@@ -188,7 +189,7 @@ public:
    /// Throws an exception if the axes configurations are not identical.
    ///
    /// \param[in] other another histogram that must not be modified during the operation
-   void AddAtomic(const RHist<BinContentType> &other)
+   void AddAtomic(const RHist &other)
    {
       fEngine.AddAtomic(other.fEngine);
       fStats.AddAtomic(other.fStats);
@@ -206,9 +207,9 @@ public:
    /// Copying all bin contents can be an expensive operation, depending on the number of bins.
    ///
    /// \return the cloned object
-   RHist<BinContentType> Clone() const
+   RHist Clone() const
    {
-      RHist<BinContentType> h(fEngine.Clone());
+      RHist h(fEngine.Clone());
       h.fStats = fStats;
       return h;
    }
diff --git a/hist/histv7/inc/ROOT/RHistAutoAxisFiller.hxx b/hist/histv7/inc/ROOT/RHistAutoAxisFiller.hxx
index 8ce974fb9ce66..40a5fc456c6bd 100644
--- a/hist/histv7/inc/ROOT/RHistAutoAxisFiller.hxx
+++ b/hist/histv7/inc/ROOT/RHistAutoAxisFiller.hxx
@@ -10,12 +10,14 @@
 #include "RWeight.hxx"
 
 #include <algorithm>
+#include <cassert>
 #include <cmath>
 #include <cstddef>
 #include <cstdint>
 #include <limits>
 #include <optional>
 #include <stdexcept>
+#include <type_traits> // for std::conditional_t
 #include <utility>
 #include <vector>
 
diff --git a/hist/histv7/inc/ROOT/RHistConcurrentFiller.hxx b/hist/histv7/inc/ROOT/RHistConcurrentFiller.hxx
index a9131fb0f4590..4f5d7e0c6b336 100644
--- a/hist/histv7/inc/ROOT/RHistConcurrentFiller.hxx
+++ b/hist/histv7/inc/ROOT/RHistConcurrentFiller.hxx
@@ -6,9 +6,7 @@
 #define ROOT_RHistConcurrentFiller
 
 #include "RHist.hxx"
-#include "RHistEngine.hxx"
 #include "RHistFillContext.hxx"
-#include "RWeight.hxx"
 
 #include <exception>
 #include <memory>
@@ -56,10 +54,10 @@ public:
       }
    }
 
-   RHistConcurrentFiller(const RHistConcurrentFiller<BinContentType> &) = delete;
-   RHistConcurrentFiller(RHistConcurrentFiller<BinContentType> &&) = delete;
-   RHistConcurrentFiller<BinContentType> &operator=(const RHistConcurrentFiller<BinContentType> &) = delete;
-   RHistConcurrentFiller<BinContentType> &operator=(RHistConcurrentFiller<BinContentType> &&) = delete;
+   RHistConcurrentFiller(const RHistConcurrentFiller &) = delete;
+   RHistConcurrentFiller(RHistConcurrentFiller &&) = delete;
+   RHistConcurrentFiller &operator=(const RHistConcurrentFiller &) = delete;
+   RHistConcurrentFiller &operator=(RHistConcurrentFiller &&) = delete;
 
    ~RHistConcurrentFiller()
    {
diff --git a/hist/histv7/inc/ROOT/RHistEngine.hxx b/hist/histv7/inc/ROOT/RHistEngine.hxx
index 02c1038dedb29..9a5e02f27e6ae 100644
--- a/hist/histv7/inc/ROOT/RHistEngine.hxx
+++ b/hist/histv7/inc/ROOT/RHistEngine.hxx
@@ -100,21 +100,21 @@ public:
    ///
    /// Copying all bin contents can be an expensive operation, depending on the number of bins. If required, users can
    /// explicitly call Clone().
-   RHistEngine(const RHistEngine<BinContentType> &) = delete;
+   RHistEngine(const RHistEngine &) = delete;
    /// Efficiently move construct a histogram engine.
    ///
    /// After this operation, the moved-from object is invalid.
-   RHistEngine(RHistEngine<BinContentType> &&) = default;
+   RHistEngine(RHistEngine &&) = default;
 
    /// The copy assignment operator is deleted.
    ///
    /// Copying all bin contents can be an expensive operation, depending on the number of bins. If required, users can
    /// explicitly call Clone().
-   RHistEngine<BinContentType> &operator=(const RHistEngine<BinContentType> &) = delete;
+   RHistEngine &operator=(const RHistEngine &) = delete;
    /// Efficiently move a histogram engine.
    ///
    /// After this operation, the moved-from object is invalid.
-   RHistEngine<BinContentType> &operator=(RHistEngine<BinContentType> &&) = default;
+   RHistEngine &operator=(RHistEngine &&) = default;
 
    ~RHistEngine() = default;
 
@@ -187,7 +187,7 @@ public:
    /// Throws an exception if the axes configurations are not identical.
    ///
    /// \param[in] other another histogram
-   void Add(const RHistEngine<BinContentType> &other)
+   void Add(const RHistEngine &other)
    {
       if (fAxes != other.fAxes) {
          throw std::invalid_argument("axes configurations not identical in Add");
@@ -202,7 +202,7 @@ public:
    /// Throws an exception if the axes configurations are not identical.
    ///
    /// \param[in] other another histogram that must not be modified during the operation
-   void AddAtomic(const RHistEngine<BinContentType> &other)
+   void AddAtomic(const RHistEngine &other)
    {
       if (fAxes != other.fAxes) {
          throw std::invalid_argument("axes configurations not identical in AddAtomic");
@@ -225,9 +225,9 @@ public:
    /// Copying all bin contents can be an expensive operation, depending on the number of bins.
    ///
    /// \return the cloned object
-   RHistEngine<BinContentType> Clone() const
+   RHistEngine Clone() const
    {
-      RHistEngine<BinContentType> h(fAxes.Get());
+      RHistEngine h(fAxes.Get());
       for (std::size_t i = 0; i < fBinContents.size(); i++) {
          h.fBinContents[i] = fBinContents[i];
       }
diff --git a/hist/histv7/inc/ROOT/RHistFillContext.hxx b/hist/histv7/inc/ROOT/RHistFillContext.hxx
index 44e184d34854c..4ea0c286aa3a6 100644
--- a/hist/histv7/inc/ROOT/RHistFillContext.hxx
+++ b/hist/histv7/inc/ROOT/RHistFillContext.hxx
@@ -8,6 +8,9 @@
 #include "RHist.hxx"
 #include "RHistEngine.hxx"
 #include "RHistStats.hxx"
+#include "RWeight.hxx"
+
+#include <tuple>
 
 namespace ROOT {
 namespace Experimental {
@@ -37,10 +40,10 @@ private:
 
    /// \sa RHistConcurrentFiller::CreateFillContent()
    explicit RHistFillContext(RHist<BinContentType> &hist) : fHist(&hist), fStats(hist.GetNDimensions()) {}
-   RHistFillContext(const RHistFillContext<BinContentType> &) = delete;
-   RHistFillContext(RHistFillContext<BinContentType> &&) = default;
-   RHistFillContext<BinContentType> &operator=(const RHistFillContext<BinContentType> &) = delete;
-   RHistFillContext<BinContentType> &operator=(RHistFillContext<BinContentType> &&) = default;
+   RHistFillContext(const RHistFillContext &) = delete;
+   RHistFillContext(RHistFillContext &&) = default;
+   RHistFillContext &operator=(const RHistFillContext &) = delete;
+   RHistFillContext &operator=(RHistFillContext &&) = default;
 
 public:
    ~RHistFillContext() { Flush(); }
diff --git a/hist/histv7/inc/ROOT/RHistStats.hxx b/hist/histv7/inc/ROOT/RHistStats.hxx
index fcd302c0327ad..07f7504ef24e7 100644
--- a/hist/histv7/inc/ROOT/RHistStats.hxx
+++ b/hist/histv7/inc/ROOT/RHistStats.hxx
@@ -6,7 +6,6 @@
 #define ROOT_RHistStats
 
 #include "RHistUtils.hxx"
-#include "RLinearizedIndex.hxx"
 #include "RWeight.hxx"
 
 #include <cmath>
@@ -14,6 +13,7 @@
 #include <cstdint>
 #include <stdexcept>
 #include <tuple>
+#include <type_traits>
 #include <vector>
 
 class TBuffer;
diff --git a/hist/histv7/inc/ROOT/RVariableBinAxis.hxx b/hist/histv7/inc/ROOT/RVariableBinAxis.hxx
index b2e0955d12fed..ea76fbe089da3 100644
--- a/hist/histv7/inc/ROOT/RVariableBinAxis.hxx
+++ b/hist/histv7/inc/ROOT/RVariableBinAxis.hxx
@@ -11,6 +11,7 @@
 
 #include <cassert>
 #include <cstddef>
+#include <cstdint>
 #include <stdexcept>
 #include <string>
 #include <utility>