diff --git a/reader/HDF5MetadataSource.cpp b/reader/HDF5MetadataSource.cpp
index f05b2596d..fa47c4232 100644
--- a/reader/HDF5MetadataSource.cpp
+++ b/reader/HDF5MetadataSource.cpp
@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: GPL-3.0-only
 
 #include <cmath>
+#include <cstring>
 #include <set>
 
 #include "HDF5MetadataSource.h"
@@ -1212,8 +1213,17 @@ std::optional<GoniometerAxis> HDF5MetadataSource::ReadAxis(HDF5Object *file, con
             return {};
     } else if (!legacy_group) {
         return {};
-    } else if (name.find("_end") != std::string::npos || name.find("_range") != std::string::npos) {
-        return {};   // the same companion datasets, by name, since there is no tag to go on
+    } else {
+        // The same companion datasets, recognised by name because there is no tag to go on. In the
+        // legacy layout each axis NAME carries five of them - AXIS_end, _start, _increment,
+        // _range_average, _range_total - and only the bare name is the axis itself. Matching the
+        // suffix rather than "contains an underscore" keeps a genuine two_theta axis readable.
+        static const char *const companions[] = {"_end", "_start", "_increment",
+                                                 "_range_average", "_range_total"};
+        for (const char *suffix: companions)
+            if (name.size() > strlen(suffix)
+                    && name.compare(name.size() - strlen(suffix), strlen(suffix), suffix) == 0)
+                return {};
     }
 
     std::vector<double> end = file->ReadOptVector<double>(dname + "_end");