diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6a3a017f..a289728e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -356,6 +356,32 @@ if (nexus)
       message(FATAL_ERROR "HDF4 library not found. Please install libhdf4-dev or hdf-devel")
     endif()
 
+    # HDF4 4.4.0 changed the Vgetname() prototype from
+    #   int32 Vgetname(int32 vkey, char *vgname)
+    # to
+    #   int32 Vgetname(int32 vkey, char *vgname, size_t *buf_size)
+    # (a fix for a buffer-overflow issue). Detect which one is present so
+    # PNeXus.cpp can call the right form for both old and new HDF4 releases.
+    include(CheckCXXSourceCompiles)
+    set(CMAKE_REQUIRED_INCLUDES ${HDF4_INCLUDE_DIRS})
+    set(CMAKE_REQUIRED_LIBRARIES ${HDF4_LIBRARIES})
+    check_cxx_source_compiles("
+      #include <mfhdf.h>
+      int main() {
+        int32 vkey = 0;
+        char name[64];
+        size_t buf_size = sizeof(name);
+        Vgetname(vkey, name, &buf_size);
+        return 0;
+      }
+    " HDF4_VGETNAME_HAS_BUFSIZE)
+    unset(CMAKE_REQUIRED_INCLUDES)
+    unset(CMAKE_REQUIRED_LIBRARIES)
+
+    if (HDF4_VGETNAME_HAS_BUFSIZE)
+      add_compile_definitions(HDF4_VGETNAME_HAS_BUFSIZE)
+    endif (HDF4_VGETNAME_HAS_BUFSIZE)
+
     add_compile_definitions(HAVE_HDF4)
   endif (HAVE_HDF4)
   add_compile_definitions(PNEXUS_ENABLED)
diff --git a/src/external/nexus/PNeXus.cpp b/src/external/nexus/PNeXus.cpp
index 77b31981..a0b7dd74 100644
--- a/src/external/nexus/PNeXus.cpp
+++ b/src/external/nexus/PNeXus.cpp
@@ -157,6 +157,28 @@ std::string nxs::getIso8601TimestampLocal() {
 }
 
 #ifdef HAVE_HDF4
+namespace {
+/**
+ * @brief Portable wrapper around HDF4's Vgetname().
+ *
+ * HDF4 4.4.0 changed the Vgetname() prototype from
+ * `int32 Vgetname(int32 vkey, char *vgname)` to
+ * `int32 Vgetname(int32 vkey, char *vgname, size_t *buf_size)` (a fix for a
+ * buffer-overflow issue). HDF4_VGETNAME_HAS_BUFSIZE is set by CMake based on
+ * a compile-time check of the header actually in use, so this call works
+ * against both old (< 4.4.0) and new (>= 4.4.0) HDF4 releases.
+ */
+int32 Vgetname_portable(int32 vkey, char *vgname, size_t bufSize)
+{
+#ifdef HDF4_VGETNAME_HAS_BUFSIZE
+  return Vgetname(vkey, vgname, &bufSize);
+#else
+  (void)bufSize;
+  return Vgetname(vkey, vgname);
+#endif
+}
+} // namespace
+
 //=============================================================================
 // nxH4::PNeXusDeadTime Constructor
 //=============================================================================
@@ -2633,7 +2655,7 @@ int32 nxH4::PNeXus::FindDatasetRefByPath(const std::string& path)
         int32 vg_id = Vattach(fFileId, vgroup_refs[i], "r");
         if (vg_id != FAIL) {
           char vg_name[VGNAMELENMAX];
-          if (Vgetname(vg_id, vg_name) != FAIL) {
+          if (Vgetname_portable(vg_id, vg_name, sizeof(vg_name)) != FAIL) {
             if (CaseInsensitiveEquals(vg_name, components[0])) {
               current_vg_ref = vgroup_refs[i];
               Vdetach(vg_id);
@@ -2667,7 +2689,7 @@ int32 nxH4::PNeXus::FindDatasetRefByPath(const std::string& path)
           int32 child_vg_id = Vattach(fFileId, ref, "r");
           if (child_vg_id != FAIL) {
             char child_name[VGNAMELENMAX];
-            if (Vgetname(child_vg_id, child_name) != FAIL) {
+            if (Vgetname_portable(child_vg_id, child_name, sizeof(child_name)) != FAIL) {
               if (CaseInsensitiveEquals(child_name, components[comp_idx])) {
                 current_vg_ref = ref;
                 found = true;